Sam Hammam has taken Cardiff from the third division to the first

The letter pledges the club's support to Mr Goodway and what it describes as "his fellow members".

Cardiff Council, led by Mr Goodway, has approved plans for the club's new stadium near its Ninian Park ground.

Opposition parties claim the letter is canvassing Labour support ahead of the council elections on 10 June.

The letter, which has been sent to about 20,000 fans, says Mr Goodway's council had made the new stadium possible.

The people who support this project are the people who want to move Cardiff forward and from whatever political party they should be supported Sam Hammam

"I want you to know they have supported us and we unreservedly support him, as you should to ensure they can finish with us the fantastic project we have started."

It describes the "detractors" that Mr Goodway has stood up to over the project as "those who would stop all development because of their negative petty politics, but he has not folded under the pressure."

But Mr Hammam said it was wrong to suggest he was urging fans to vote Labour, simply because of his admiration for Mr Goodway.

"Russell Goodway is the leader - he is a Labour man, but there are other people in the council other than Labour," Mr Hammam told BBC Wales' Dragon's Eye programme.

"The people who support this project are the people who want to move Cardiff forward and from whatever political party they should be supported."

The stadium is due to open in 2006

The former owner of Wimbledon FC bought Cardiff in August 2000 and has revitalised the club, taking it from the third division to the upper half of the first division.

But he has insisted that the club's further progress depends on its new 30,000-capacity stadium - with potential to rise to 60,000 - just over the road from its existing home, Ninian Park.

Mr Hammam told Dragon's Eye that far from being Labour supporter, he was an "ultra-right conservative capitalist".

A spokesman for Labour welcomed the letter.

"Mr Hammam can speak for himself, but we're glad he's recognised our hard work and achievements for football supporters, and also for local residents."

But Conservative AM Jonathan Morgan said sending the letter was a "stupid decision".

'Unwise' letter

"He wants its fans to support city and the council - it is pretty clear what the intention is."

"There's all-party agreement on the stadium - it is dangerous to line yourself up with the ruling party."

Liberal Democrat AM for Cardiff Central Jenny Randerson said that, although Mr Hammam had done nothing wrong, the letter might have to be registered as an election expense by Labour.

"I have great support for his [Mr Hammam's] football judgement, but I really doubt his political judgement," she said.

Plaid Cymru AM Owen John Thomas said he did not think the letter was a good move.

"I think he's been unwise to put out a letter where there are five different references which are, more or less, asking people to support the Labour Party at the next elections.