Albion spurned the chance to put pressure on the two teams above them at rainswept Withdean.

Mark McGhee's men were good value for an interval lead provided by Leon Knight's 17th goal of the season from the penalty spot after 16 minutes.

An inspired substitution by Vale boss Brian Horton changed the complexion of the contest.

The former Albion captain and manager brought on Adrian Littlejohn for the second half in place of Andreas Lipa, who conceded the penalty by fouling Chris McPhee.

Littlejohn levelled on 50 minutes to deny the Seagulls a hat-trick of League wins.

Albion had to cope without both Danny Cullip (groin) and Richard Carpenter (hamstring) for the first time since May 2001.

Robbie Pethick continued in the centre of defence in place of Cullip, while young loanees Mark Yeates and Zesh Rehman partnered each other in the middle of the park in the absence of Carpenter.

Nathan Jones and Gary Hart were back on the flanks following the LDV Vans Trophy exit at Queens Park Rangers.

Horton made three changes to the Vale team after they were knocked out of the FA Cup by Conference club Scarborough. The fit-again Stephen Brooker, Neil Brisco and Steve Rowland returned at the expense of Littlejohn, Liam Burns and Levi Reid.

Chris McPhee went close to continuing his rich vein of goalscoring form for Albion inside the opening minute when he headed narrowly wide from a free-kick by Pethick.

The playing surface was slippery on top and several players had problems keeping their footing early on.

A corner by Mark Boyd for the visitors caused some problems for the Seagulls defence before Guy Butters, captaining the side, cleared.

Loose marking by Vale allowed Knight to find space towards the far post from Pethick's cross, but his shot was blocked by defenders.

The Seagulls' bright start was soon rewarded. McPhee fed Hart to his right and his shot was parried by Jon Brain, Vale's 18-year-old custodian. The ball broke to McPhee inside the box and he was brought down by Austrian midfielder Lipa.

Premiership referee Rob Styles pointed to the spot and Knight checked his run-up before sending Brain the wrong way.

Knight's previous goal at Withdean also came from the penalty spot in the 4-1 drubbing by Bristol City last month. It was a nice way for Albion's little frontman to mark his final home appearance of the year.

He is suspended for the game against Wycombe on Boxing Day following a controversial fifth caution of the season at QPR.

Albion were forced into a change in the 27th minute. Hart, who was signed for the Seagulls by Horton, failed to recover from an earlier knock so John Piercy took his place on the right side of midfield.

Roberts' distribution left a little bit to be desired, a couple of throw-outs zipping away from their intended targets.

Albion's keeper, seeking consecutive clean sheets at home, was seen to do better when he dived full length to cut out a cross by Michael Cummins. Albion tried to stretch their advantage with a setpiece routine straight off the training ground, Piercy and McPhee forming a two- man barrier in front of the Vale wall for a free-kick 25-yards out.

They split as Jones ran up to shoot, but the Welshman's effort was headed clear by Cummins.

Vale came into the match a little more in the closing stages of the first half.

Styles, having issued 34 yellow cards in seven premiership matches this season, booked Kerry Mayo and Billy Paynter when they clashed.

Roberts took no chances in first half stoppage time when he tipped over a right-wing cross from Boyd which was dipping under the bar.

Vale introduced Littlejohn for Lipa for the second half and the substitute almost made an immediate impact. A mistake by Adam El-Abd let in the forward, but his toe-poke was smothered by Roberts.

Butters almost put Albion further ahead after Brisco had his name taken for holding back Yeates. Butters met Mayo's resulting free kick with a header which Brain pushed for a corner.

Vale went straight up the other end to grab a surprise equaliser with a fine individual effort by Littlejohn. The veteran replacement ended a jinking run with a low left foot drive from 25-yards which sped past Roberts.

Vale were looking much brighter as an attacking force with the introduction of Littlejohn.

A cross by Piercy which threatened to drop into the net was touched behind by Brain after good approach work from Knight.

Vale brought on Mark Bridge-Wilkinson for Brooker as the match moved towards an intriguing climax. Albion responded by introducing Dave Lee for Jones, with Piercy switching from the right to the left-flank.

Roberts almost gifted Vale the lead when, trying another throw-out, he held on to the ball for too long and ended up throwing it backwards.

The keeper recovered by diving at the feet of Steve McPhee.

Rehman went close in the dying stages with a couple of headers. The first from Yeates' corner cleared the bar and the second, from Piercy's cross, struck the woodwork.

Vale nearly snatched victory with a minute left when Littlejohn's shot was parried upwards by Roberts and McPhee, following up, headed against the bar.

ALBION (4-4-2): Roberts (gk) 6; Mayo (lb) 6, Pethick (cd) 7, Knight (f) 7, Hart (rm) 6, Yeates (cm) 7, Butters (cd) 8, Jones (lm) 6, McPhee (f) 7, El-Abd (rb) 7, Rehman (cm) 6. Subs: Peircy 6 for Hart (injured 27), Lee for Jones (withdrawn 67), Hinshelwood, Harding, Keeley.

Scorer: Knight (16) pen.

Bookings: Mayo (42 unsporting behaviour) Rehman (85 unsporting behaviour).

PORT VALE (4-3-3): Brain; Pilkington, Lipa, Collins, Brisco, Cummins, Brooker, S. McPhee, Boyd, Rowland, Paynter. Subs: Goodlad, Bridge-Wilkinson for Brooker (withdrawn 65), Reid, Littlejohn for Lipa (withdrawn 46), Burns.

Scorer: Littlejohn (50).

Bookings: Paynter (42 unsporting behaviour), Brisco (48 foul).

Half-Time: Albion 1 Port Vale 0.

Attendance: 5,811.

Fan's view: Steve Brighton (Littlehampton).

On a wet and miserable night, I felt we shaded the game overall. However, Port Vale got players behind the ball and we didn't have enough spark to make our possession count and turn one point into three to pile the pressure on the teams above us.

We don't seem to be able to build from midfield like we used to do but since Bobby Zamora left the whole shape of the side has changed.

Mark McGhee has my 100 per cent support. He realises that a few players have become lacklustre over the past couple of seasons and is using the loan signings well to improve us. I can't fault the effort on the night and we did enough to have won.