The Political Animal Lobby (Pal), which hoped Labour would ban fox hunting, has secretly paid half of the Green Party's European election campaign costs - the biggest single donation it has ever received.
Insiders say that the wealthy lobbying organisation feels that the Labour government has failed to live up to expectations on animal rights issues.
Animal welfare groups, which gave public support to Labour MPs before the last election, privately feel betrayed by Mr Blair's decision not to use his huge parliamentary majority to push through a law banning fox hunting with hounds.
In its election manifesto, Labour pledged to allow a free Commons vote on hunting, and many supporters believed that it would follow this up with action banning the sport.
"What is the point of having a free vote if you don't reflect the vote with appropriate legislation?" said Charlotte Morrissey, of the RSPCA.
Most Labour MPs are in favour of outlawing fox hunting, but the Prime Minister is said to have been taken aback by the scale of massive marches in London staged by the pro-hunting Countryside Alliance since Labour came to office.
Pal, which has refused to comment on the apparent change in allegiance, was founded in 1990 to channel funds to political parties most likely to back animal welfare laws. The Green Party, which does not yet have any MEPs, has a wide-ranging policy on animal welfare, including the banning of vivisection, fur farming, circus animals and all hunting.
Pal wrote out a cheque to the Green Party for pounds 50,000 during a private meeting at its London offices in March. "This donation is a blessing to us," said a spokesman for the Greens.
The deal was brokered by Kevin Saunders, a leading light in the anti- hunting lobby, who is now a full-time employee of the Green Party. Present at the meeting were Mr Saunders, formerly of the League Against Cruel Sports, Gareth Edwards, a fundraiser for the Green Party, and Brian Davies, who set up the Political Animal Lobby and also founded the International Fund for Animal Welfare.Reuse content