Former Beatle Paul McCartney and his second wife, Heather Mills McCartney, said Wednesday that they are separating after nearly four years of marriage, blaming intrusion from the media and insisting their split is amicable.

Rumors of a rift between Mills McCartney and the singer's children — especially Stella McCartney — have circulated for years. Talk centered around the idea that Mills McCartney — who is nearly half his age — wanted to devote more time to campaigning against land mines and fur.

"Having tried exceptionally hard to make our relationship work given the daily pressures surrounding us, it is with sadness that we have decided to go our separate ways," a statement from the couple said. "Our parting is amicable and both of us still care about each other very much."

McCartney, 63, and Mills, 38, married in June 2002, four years after his former wife, Linda McCartney, died of breast cancer. McCartney and Mills had a daughter, Beatrice, in October 2003.

"Separation for any couple is difficult enough, but to have to go through this so publicly, especially with a small daughter, is immensely stressful," it added. "We hope, for the sake of our baby daughter, that we will be given some space and time to get through this difficult period."

McCartney's wealth was estimated at $1.5 billion by the Sunday Times in their annual list of Britain's richest people. The couple are believed not to have a prenuptial agreement.

Speculation immediately arose about the size of a possible settlement, with lawyers estimating Mills McCartney's share of the former Beatle's fortune at between $188 million and $376 million.

On Wednesday afternoon, McCartney posted a message on his personal Web site, saying he was very upset over suggestions that Mills McCartney had married him for his money.

"It's been suggested that she married me for the money and there is not an ounce of truth in this," he said in the post. "She is a very generous person who spends most of her time trying to help others in greater need than herself. All the work she does is unpaid, so these stories are ridiculous and completely unfounded. I'm very sad to see that some insensitive people would choose a moment like this to spread these vicious rumors."

In 2002, Heather Mills told Vanity Fair that McCartney didn't force her to sign a prenuptial agreement before their huge wedding — despite tabloid reports to the contrary.

Mills said she offered to sign an agreement, but that McCartney — who was worth more than $1 billion at the time — wouldn't allow it.

"I wanted to prove that I love him for him," she was quoted by the magazine as saying. "He said, 'I wouldn't let you."'

McCartney told the magazine that he knew some people would think he was being suckered by a gold digger.

"I"m not stupid," he told Vanity Fair. "Heather's a really nice person, or else I wouldn't be attracted in the least. She's great. But you're going to find people who are going to knock her, because the better story is the negative one."

Mills McCartney has been accused of meddling in her husband's career — such as the dismissal of his longtime publicist Geoff Baker — and even of influencing him on issues as diverse as dying his hair and plastic surgery.

In a statement on her personal Web site, Mills McCartney posted a note from McCartney blasting the press and denying the rumors.

"Although some of these articles can be funny, there are others that are plain malicious and you need to be strong not to be hurt by some of the cruel suggestions that flow from these peoples pens," the statement said.

"The media sometimes suggests a rift between my kids and Heather, but in fact we get on great and anyone who knows our family can see this for themselves," McCartney wrote.

Mills is a former model and a vociferous animal rights campaigner who recently traveled with McCartney to eastern Canada to fight that country's seal hunt. The couple met in 1999 through Mills' charity, the Heather Mills Health Trust. She launched the trust after losing a leg in a motorcycle accident in 1993.

News of the split was first reported in Wednesday's edition of the Daily Mirror.

McCartney already has three children from his marriage to Linda, who died in 1998 — musician James, photographer Mary, and fashion designer Stella. He also has a stepdaughter, Heather, from Linda McCartney's first marriage.