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MANCHESTER, England (Reuters) - Britain wants to negotiate a Brexit agreement with the European Union, but is ready to walk away with no deal, Brexit minister David Davis said on Tuesday, warning that any error in the talks could cost them billions of pounds.

At the annual conference of the Conservative Party, Davis told members the government did not want to fail in the talks to unravel more than 40 years of union, but officials were “contingency planning” to make sure all scenarios were covered.

British Prime Minister Theresa May has tried to unblock the talks with EU leaders, after they stalled over disagreements on the final divorce bill, by making concessions on the role of the European court and the financial settlement.

But earlier on Tuesday, the European Parliament passed a non-binding motion calling on EU leaders to conclude at a summit on Oct. 19-20 that Brexit talks had not made sufficient progress to justify opening trade negotiations with Britain.

“On the negotiating front, we are aiming for a good deal. And that is what we expect to achieve. However, if the outcome of the negotiation falls short of the deal that Britain needs we will be ready for the alternative,” Davis said.

“That is what a responsible government does. Anything else would be a dereliction of duty.”

Davis, who said Britain was nearing agreement with the EU on citizens rights - one of three issues to be settled in the first round of negotiations, criticized the main opposition Labour Party for having an unclear position on Brexit

“This is the most complex negotiation you could imagine, where one oversight, one error could cost the taxpayer billions of pounds,” he said.