Heather Mills' former nanny has told an employment tribunal that she made all her staff's lives a misery but she was the only one prepared to speak out.

Sara Trumble, 26, alleges that Mills forced her to say positive things about her to a film crew and made her work long hours without any extra pay.

She also claims her former employer made her feel uncomfortable by moaning to her about ex-husband Sir Paul McCartney and was unsympathetic towards her when she went though a difficult pregnancy, forcing her to accompany her on trips abroad.

During cross-examination from Mills solicitor, Caroline Crampton-Thomas, on the second day of the hearing, Ms Trumble said: "I wasn't the only person who felt that at that time. It's just that nobody else will stand up. I decided to take action and fight this for myself."

Ms Trumble, who was paid £260 a week to look after Beatrice, now six, said she was close to former model Mills when she began working for her in April 2004 but she became rude and bad-tempered after she split from the former Beatle.

She told the tribunal in Ashford, Kent, that all of Mills' staff, which included her housekeeper, her personal trainer Ben Amigoni, a bodyguard and her personal assistant, noticed a change.

She added that they were all under great pressure to make sure Mills new nine-bedroom home in Robertsbridge, East Sussex, was ready for her when it underwent a full refurbishment in August 2007.

Mills, who sat at the back of the tribunal room wearing thick-rimmed glasses, a grey pinstripe suit jacket, black trousers and a pink shirt, whispered to friends throughout the hearing.

She also kept angrily walking over to speak in her solicitor's ear, at one point prompting her sister, Fiona, to tell her to sit down.

Ms Trumble is seeking compensation from Mills on the grounds of sex discrimination and unfair dismissal and also claims she suffered changes to her employment terms following her maternity leave.

Ms Trumble was questioned over claims that she received a £10,000 pay-off from Sir Paul after she resigned in September 2008.

She said the money was a gift "for my dedication and hard work with Beatrice" and she declined it "several times" before eventually accepting.

"Paul did not want anybody to know that he gave me this money.

"I don't want to get Paul involved so it's difficult to talk about this money," she said.

She said Mills made her feel "awkward" by making her lie to Sir Paul about where she was when she met him to collect or drop off Beatrice.

Ms Trumble also described how at these times Mills would send out her new boyfriend, Jamie Walker, to flaunt him to her ex-husband.

Ms Trumble admitted that Mills was often generous towards her, giving her several monetary gifts along with a Daihatsu Copen convertible as well as baby clothes and accessories when she had her daughter.

She also acknowledged that Mills took her to Slovenia along with her other staff and friends to celebrate her 39th birthday and she was invited to join the charity campaigner on a holiday to Sir Richard Branson's private Caribbean island, Necker, although she did not go as she had only just had her baby.

But she disputed that Mills took her on numerous shopping trips for clothes, adding: "She bought me one top, and on another occasion it was a 'buy one, get one free' top she bought me."

Questioned about why she wanted to leave the job, she said: "It's not all about money, I'm not talking about gifts and all that she gave me.

"It's about how she treated me.

"It wasn't a nice environment to work in. I was always going home upset, sometimes it was the way I was spoken to."

Asked by Ms Crampton-Thomas why she refused to sign a further confidentiality agreement after she resigned, Ms Trumble said she felt she did not need to as she had already signed numerous forms and was no longer under Mills's employment.

She denied she had ever gone to the press and said she did not know who was responsible for an article which appeared about her in the Sunday Mirror.

"I had nothing to do with the press during my employment with the McCartneys," she said.

Mills is expected to give evidence later this afternoon.