As Mr Livingstone was installed as the bookies' favourite for the race, his campaign team complained that he was being "smeared" in a Dobson leaflet distributed to party members in the capital.
The Dobson camp received further support yesterday when the Iron and Steel Trades Confederation voted to back the former health secretary in the election race.
Tony Blair also sought to increase the pressure on Mr Livingstone with an article in the London Evening Standard claiming that the rebel MP was a throwback to the era of Arthur Scargill and Tony Benn.
The Dobson campaign leaflet lists the former GLC leader's supporters as Lord Archer of Weston-super-Mare, the Tory candidate, former council chief "Red Ted" Knight, and the Socialist Workers Party.
A spokesman for the Livingstone camp said last night that the leaflet was a clear breach of the party's rules.
"Candidates or their agents shall not use the media to attack or denigrate other candidates," the rules state.
"This is a new low in Labour Party selection contests. This leaflet is dirty and shoddy. Heads will have to roll in the Dobson camp," he said.
A spokesman for Mr Dobson said the leaflet was a political rather than a personal attack, and was justified. Some 38 London Labour MPs signed up to the former Health Secretary's campaign yesterday.
After taking pounds 10,000 of bets on the Brent East MP yesterday morning, William Hill cut his odds from 5/4 to 10/11, and lengthened the previous favourite, Frank Dobson, from 10/11 to 5/4 second favourite. Hill's offered Lord Archer at 6/1, Glenda Jackson at 25/1, and Susan Kramer, the Liberal Democrat candidate, at 100/1.
Mr Dobson backed a trade union campaign to boycott Lufthansa flights on behalf of workers sacked by the airline for going on strike. He said the company had acted "unreasonably" in dismissing the largely Asian workforce at its part-owned subsidiary Skychefs at Heathrow. "They couldn't get away with sacking these workers in Berlin and they shouldn't get away with it in London. I will be supporting the TUC-backed call for Londoners to boycott Lufthansa airlines until the company sees sense and reinstates these workers," Mr Dobson said.
But Mr Dobson's written statement in favour of the staff will be upstaged today by Mr Livingstone, who will be speaking at a rally in Hammersmith Town Hall to mark the first anniversary of the dispute.
Both men are urging the company to reinstate the 270 workers who were dismissed after a lawful day-long stoppage last November. The law has since been changed to prevent employers sacking workers taking lawful industrial action.
The staff voted by a 75 per cent majority to strike over the company's unilateral introduction of new working patterns, which eliminated overtime payments and meant different starting times.Reuse content