Mr Zeman (left) also discussed EU enlargement
During a brief visit to the Czech Republic last week the prime minister promoted the sale of Gripen jet fighters which are made by an Anglo-Swedish consortium including Labour donor BAE systems.
Now a spokesman for Mr Blair said that "bearing in mind the hoo-ha in the Sunday papers" maybe they should have told journalists that the jets featured in the talks.
The spokesman said: "The world would be turned on its head if the prime minister did not go into bat for one of the largest British contractors."
"He believes it would have been a dereliction of his job not to do it."
Labour's relationship with business has been under the microscope since its links with Indian steel tycoon Lakshmi Mittal were revealed earlier this year.
Mr Blair was accused of helping Mr Mittal buy Romania's state steel industry in return for a £125,000 party donation.
'No apology'
Last week questions were raised about the awarding of a lucrative government contract to supply smallpox vaccine to PowderJect, a company headed by a Labour donor.
Downing Street has said there was nothing untoward in either case.
It has angrily dismissed the latest "cash for favours" allegations, made in a Sunday newspaper.
A Downing Street spokesman said the prime minister "makes no apology for promoting Britain and British business".
Millennium Dome
Mr Blair's flying visit to Czech capital Prague was made as he returned from talks with US President George Bush in Texas.
Downing Street said that the key issue on the agenda for talks with Czech Prime Minister Milos Zeman was European Union enlargement.
But a spokesman said that other bi-lateral issues were discussed, including the proposed purchase of 24 JAS-39 Gripen jets by the Czech government.
BAE Systems, which has a share in the fighter, paid £12m in sponsorship for the Millennium Dome and donated more than £5,000 to Labour in 1998-99 and 1999-2000.
Inquiry call
Shadow Cabinet Office minister Tim Collins told the Independent on Sunday there should be a full inquiry.
"Once again, the government in general and the prime minister in particular is found to have undertaken extraordinary efforts on behalf of an organisation which has done favours for the Labour Party," he said.
He called for an "independent mechanism" to be set up to investigate such cases.