The Foreign Secretary has warned Spain over its refusal to allow cruise ships which have visited Gibraltar to dock in Spanish ports.
Britain regards the cruise ship boycott as illegal
Jack Straw issued the warning after talks with his Spanish counterpart Miguel Angel Moratinos in London.
"I spelled out to the minister that we regard the disruption to the cruise ships as unacceptable," Mr Straw said.
The authorities in Gibraltar revealed on 6 May that Spanish ports had been refusing to allow the vessels to dock.
The row is viewed by Gibraltar as part of the ongoing dispute between Britain and Spain over the sovereignty of the territory.
Officials claim the move is an attempt by Spain's new
Socialist government to strangle the colony's economy.
Legal action possible
Britain regards the cruise liner boycott as illegal, and has not ruled out legal action as a last resort.
Mr Moratinos, on his first official visit to Britain, said he hoped the situation would be resolved, but did not offer a solution.
"I do not see there being any chaos between Great Britain and Spain," Mr Moratinos said.
"We discussed the problem of Gibraltar as one of the normal points of the agenda between the UK and Spain."
This year, Gibraltar has been celebrating the 300th anniversary of its capture from Spain.
London and Madrid came close to an agreement on joint sovereignty in 2002, but negotiations collapsed after an unofficial referendum of Gibraltar residents rejected the plan.
Mr Straw has said that Britain will not cede the territory to Spain without the consent of its people.
Mr Moratinos did not offer a date for the resumption of talks on the status of the territory.