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A spokesman for the prime minister said Lord Sutch, "will be much missed. For many years he made a unique contribution to British politics.

"Our elections will never be quite the same without him."

A Scotland Yard spokesman said Lord Sutch, whose real name was David Sutch had been found hanged.

Leon Hawthorne reports: "His girlfriend found him hanging"

A post-mortem has yet to take place and initially the death is being treated as suspicious.

Ms Elwood said: "It is a terrible shock because we envisaged spending the rest of our lives together and it is something that is very hard to come to terms with."

Although he fought a long-term battle with depression, the party leader had seemed happy in the days leading up to his death, Ms Elwood, 41, said.

But she admitted: "He did suffer from depression but that was a very long-term complaint, of many years."

His friend Alan Hope said he had received the news from Ms Elwood.

John Pienaar reports: "He made it impossible to take politics too seriously'

Mr Hope, who became the first Loony mayor, at Ashburton Town Council in Devon, said: "I'm absolutely devastated - the whole party is going to be. The Monster Raving Loony Party is Screaming Lord Sutch."

The maverick politician became Britain's longest serving party leader after launching the Monster Raving Loonies in 1963.

Mr Hope has now taken over the leadership of the party temporarily until a new leader can be endorsed by the party at its conference in September.

David Sutch: Fought a long battle with depression

Mr Hope is leading calls for a statue to be erected to Lord Sutch outside Parliament next to the statue of Sir Winston Churchill - one of the Loony leader's heroes.

Mr Hope, who runs the party headquarters from the Golden Lion pub in Devon, said his friend had been in good spirits when they spoke on the telephone 10 days ago.

"He was saying he had no money troubles any more, and was sorting out his life and was looking forward to coming down here next weekend."

Mr Hope told the BBC: "I've known David since 1957 - we were rock'n'roll singers together.

"He was a hell of a character."

Mainstream politicians have also paid tribute to the man who was always keen to inject humour into a frequently dull business.

Shadow Chancellor Francis Maude said: "He was a great eccentric on the edge of politics."

Harry Greenway, the former Tory MP for Ealing North, who was a close friend of Lord Sutch, described him as "the man who brought gaiety to politics and who pricked the pomposity of politicians".

E-mail tributes

E-mails paying tribute to Lord Sutch have been received by BBC News Online from across the world.

Conservative MP Nigel Evans e-mailed saying: "I fought the Ribble Valley by-election in 1991 and Lord Sutch entered the race. He brought a sense of fun and ridicule to what for the rest of the main candidates was cut throat.

"He was the original and clearly the best. You felt you hadn't really fought a by-election unless Lord Sutch was on the ballot. MPs of all parties will miss him."

Councillor Greg Stone from Newcastle e-mailed saying: "As a local politician myself, I have nothing but admiration for him. Given what passes for sanity in politics today, Lord Sutch was the perfect antidote."

While from Maryland in the United States Jason Tolbert praised Lord Sutch's contribution to politics.

"I hope the party keeps up the work after Sutch's death, and I wish we had a party like that here in the U.S.," he said.

Lord Sutch's musical peak was during the 1960s, when his political crusade began, but he continued playing up to 250 concerts a year up until his death.

Mother's death a blow

Lord Sutch recently suffered the loss of his mother Nancy and said the party could not afford to field any candidates in the past week's elections to the European Parliament.

He had also announced his intention to stand down as party leader.

Joyce Gray, who runs the Red Cross charity shop where Sutch occasionally worked, said Lord Sutch never recovered from his mother's death.

"The last time I spoke to him he phoned me to tell me his dog Rosie had died," she said. "He said `it's only been two years since mum died, now Rosie. What next?"'

Lord Sutch has a son Tristan, now in his 20s and living in Texas, from his relationship with American model Thann Quantrill.