Heather Mills McCartney is threatening to stalk actress Jennifer Lopez in an increasingly bitter row over animal rights.

She says she will track the fur-wearing film star to her home and confront her on the red carpet at her next movie premiere.

And the second wife of Sir Paul McCartney says the ex-Beatle has told her he is proud of what she is doing.

In opposing fur, she is taking up yet another of the causes espoused by Linda, Sir Paul's late first wife.

Miss Mills spoke yesterday after leading a group of protesters in an invasion of the New York offices of Miss Lopez's clothing company Sweetface.

The 37-year-old former model was brandishing a video that apparently showed animals being skinned alive.

However, Miss Lopez was not in the building as the demonstration by activists from PETA - People for the Ethical Treatment of Animals - took place. Miss Mills was escorted from the premises by security guards who had threatened to call the police if she did not leave. But she was unrepentant about the vociferous campaign to stop the star wearing fur and incorporating it in her fashion range.

'PETA has tried for years to educate her about fur, at first quietly and now like this,' she said. 'She keeps saying she wants to be educated. So the next stage is I'll find out where she lives and show up there. And I'll get a hold of her at her premieres.

'She needs to find some warmth inside her and penetrate that warmth in her heart.' Miss Lopez, who is also a pop singer, has became the target of animal rights groups because she often attends premieres and award ceremonies draped in fur. She has led the renaissance of fur in the fashion industry, by making it seem aspirational in the 'bling-bling' culture of young, wealthy urban Americans.

In 2002 she arrived at the opening of the film Maid in Manhattan wearing a £10,000 white mink coat - further agitating animal rights campaigners.

Yesterday's invasion was the second protest Miss Mills has taken part in this week. On Monday, she was thrown out of the New York premises of the fashion label J Crew by police after she stormed the store wearing a sandwich board containing a plasma screen television showing scenes of animals being skinned alive in China.

On Sunday, 63-year-old Sir Paul had accompanied her to a fund-raiser for PETA. Miss Mills said yesterday: 'I talked to Paul today and he's very proud.'

After marrying the pop legend in 2002, Miss Mills - who lost a leg when she was hit by a police motorcyclist in London in 1993 - initially focused her attention on her campaign to ban antipersonnel landmines.

But after some success with that crusade, she has now turned her attentions to animal rights and the promotion of vegetarianism - issues strongly associated with Linda.

Before Linda died of cancer in 1998, she and Sir Paul had been the world's highest-profile vegetarians.

Linda launched her own eponymous vegetarian foods range, which was carried by all the major supermarkets and brought vegetarian dishes to millions of British homes.