Council blunders have allowed dozens of mobile phone masts to win planning permission.

On 26 occasions councils have fallen foul of a legal loophole allowing masts to be approved because officers failed to respond to applicants in time.

A catalogue of errors uncovered through a Freedom of Information request shows councils sent decisions by second-class post, date-stamped letters incorrectly, miscalculated time periods, sent out wrong decision notices and failed to make the fact they had refused permission clear.

Gary Kemp, who lives in Brighton and campaigns against phone masts for Friends of the Earth, said: "It's an absolutely appalling record. I am 100 per cent certain that phone masts cause health problems so it makes me really angry to know masts have gone up by default.

"We have enough problems fighting masts that are granted planning permission."

Current legislation allows mobile phone companies to assume masts below 15m in height have been given planning approval if they do not hear in writing from a council within 56 days.

The council is legally obliged to write to the companies within the given time, outlining whether the mast actually needs prior approval and whether or not the council objects to its siting and appearance.

In nine of the cases involving errors the authorities intended to refuse planning permission.

Sian Meredith, a spokeswoman for campaign group Mast Sanity, said: "The figures for Sussex are just the tip of the iceberg. We deal with hundreds of these across the country.

"Planning ministers have said the current system is perfectly okay but these figures prove it is not. We think all masts should go through the proper planning process."

Brighton and Hove City Council allowed five masts to be installed because decision notices were not received on time.

Leslie Hamilton, chairman of the planning committee, said; "I know early on we did have some problems but it hasn't happened recently."

He recalled a mix-up last year over what counted as the first day of the 56-day notice period which led to the council missing the deadline by one day and permission being granted by default.

He said: "I remember there was a conscious decision made to make sure we considered these applications within the time period so companies didn't get automatic consent."

Horsham District Council admitted failing to contact phone companies 14 times although it said that each time it only intended to inform the company that approval was not needed.

A spokesman said: "All these cases relate from 1998 to 2000 and no prior approval was necessary." He said all subsequent applications in the last six years had been dealt with on time.

Arun District Council admitted that a mast was erected because a letter was sent by second class post and missed the 56-day deadline. The figures were disclosed to the BBC as part of an investigation into phone mast applications across the South.

Rachel Bridgeman, 41, of Portland Road, Hove, is a member of Together We Can Stop the Mast, which is campaigning to stop a ten-metre mast being installed by Marconi/T-Mobile in the Wish Park area.

She said: "Everyone makes mistakes but at the end of the day there should be legislation to prevent them."

She said stringent regulations should be introduced to force mobile phone companies to consult nearby schools, businesses and home owners.

John Silvester, spokesman for the Planning Officers Society, said: "It's not rocket science to work out when the period finishes. Things should not be taken to the wire."

A spokesman for the Office of the Deputy Prime Minister said: "Local planning authorities have the opportunity to deal with prior approval applications in the same way as a normal planning application, so long as they act within eight weeks."