The shadow secretary for trade and industry, Jack Cunningham, has written to Michael Heseltine, the President of the Board of Trade, to ask him to refer the £77m deal to the Monopolies and Mergers Commission, which has the power to block it.
Labour has also secured a 90-minute debate next Wednesday morning, during the course of which they will make serious allegations about the deal.
The MMC move, made as it is by such a senior member of the shadow cabinet, marks Labour's determination to fight a further extension of Murdoch's empire.
Mr Cunningham said: "Labour is deeply concerned that someone as unaccountable as Rupert Murdoch should have such great control over so many of our sports, including football, golf, cricket and boxing. The Government has an obligation to make sure that rugby league is not added to the list."
Other Parliamentary sources added that the extent of Murdoch's control of rugby league would create a dangerous precedent and, by decreeing the teams and individuals against whom players could compete, infringe their freedoms.
In his letter to Mr Heseltine, Mr Cunningham cites two grounds for a referral to the MMC: the danger of a monopoly of televised rugby league and the creation of "local monopolies" by the merger of existing clubs into new, Super League entities. Mr Cunningham has also written to Sir Bryan Carsberg, the director general of the Office of Fair Trading, to ask him to exercise his powers to recommend a referral.
Rumours that the MMC had already put a block on Murdoch and the plans of his company, News Ltd, for the game led the chairmen of Keighley and Castleford, two clubs which stand to be affected in different ways, to announce prematurely that the deal was off on Monday.
What seems certain now is that it will not go ahead without a prolonged battle. The League, whose chief executive, Maurice Lindsay, was on his way back from Australia, and whose chairman, Rodney Walker, is on holiday in Spain, would make no comment on yesterday's developments.
The Australian Rugby League chief executive, Ken Arthurson, has accused his British counterparts of jettisoning 87 years of Test rivalry by signing their exclusive deal with Super League. Great Britain, under the terms of their contract, will not be able to play Ashes Tests against official ARL teams in future.
"It is one thing for them to join the Super League, but quite another for them to have thrown that great tradition out of the window," said Arthurson after his meeting with Lindsay.
Although the meeting between the two chief executives appears to have agreed a truce that will safeguard this October's Centenary World Cup, in which England, Wales and Australia are all due to compete, the loss of Test matches is one of the most unpalatable aspects of the Murdoch deal.
Salford, hoping to win selection over Oldham for Super League membership when the structure of the new competition is finalised on 4 May, have announced plans for a new 10,000-capacity stand at The Willows.
Gateshead, mooted as a venue for a Super League side at some stage in the future, is to host its first Championship fixture on Sunday. Carlisle, who fear a mass exodus from the city for the same day's football final, the Auto Windscreens Shield involving Carlisle United at Wembley, are taking their last Second Division match of the season against Ryedale- York across the country to the International Stadium.
n Rochdale, angry that Second Division clubs were not invited to a Super League meeting of chairmen last week, said yesterday they would seek a judicial review unless the Rugby League failed to provide assurances that future decisions on the organisation of the sport will be made only in consultation with all member clubs.Reuse content