Nations opposed to commercial hunting are hopeful of gathering enough votes at the International Whaling Conference to overturn a motion passed last year calling for its resumption.

But Greenpeace accused ministers of not doing enough to persuade other countries to ensure they attended the annual summit and were able to vote.

Last year, pro-whaling nations led by Japan succeeded in passing a declaration by one vote calling for a "resumption of commercial whaling on a sustainable basis".

It was seen as a symbolic victory in a campaign to gain the 75% support needed to overturn a 20-plus-year ban on commercial whaling altogether.

Japan, Iceland and Norway all exploit loopholes to continue the practice - partly under the guise of scientific research - to the fury of campaigners.

Biodiversity minister Barry Gardiner is attending the conference amid confidence that the UK has succeeded in winning the vital backing of several more nations.

A Department for Environment, Food and Rural Affairs spokeswoman said the UK had led efforts to recruit more support to the cause.

She said: "We have already had some success: Croatia, Cyprus, Greece and Slovenia have already joined in time for this year's meeting. Peru and Costa Rica have regained voting rights, and several more EU states are indicating their intention to join in time for next year's meeting."

However Greenpeace UK oceans campaigner Willie Mackenzie said it was still unclear how much extra support the pro-whalers had mustered over the last 12 months. And he complained that Mr Blair had not met calls to write to other sympathetic leaders asking for their support, leaving such diplomatic moves until after the IWC meeting.