The Lib Dem leader has warned Labour that any future co-operation between his party and Tony Blair's government is dependent on both parties pressing ahead with voting reform.

Speaking on Sunday, Charles Kennedy said that the Lib/Lab project would end if Labour finally withdrew its commitment to develop a PR system in the UK.

"If Labour or ourselves are able to do something about getting voting reform - then let's do it. But if the issue is off the agenda then relations between the parties are firmly off the boil," he told the Frost progamme on Sunday.

Kennedy also attacked "wealthy tycoons", such as Stuart Wheeler who last week announced he was to give £5 million to the Tories, over the issue of large donations to political parties. His comments came as it emerged that Wheeler said he could not support a more pro-European Conservative Party under the leadership of former chancellor Kenneth Clarke.

Wheeler has also suggested he may give more cash to the Tories - although he poured cold water on suggestions that he may back William Hague to the tune of £10 million.