European trade watchdogs have formed a black list of objections to the merger between cruise giant P& O Princess and Carnival, a report said.

The European Commission has told US-based Carnival chiefs of a series of concerns to their �3.8bn bid for its UK, news agency Reuters said.

Carnival, the world's top ranking cruise firm, has an opportunity to respond to the criticisms, and can propose changes to the deal.

It could also demand an oral hearing into the takeover, which P&O Princess's directors have resisted in favour of a merger with Miami-based Royal Caribbean.

But P&O shareholders in February ignored their board's recommendations, and voted for extra time to consider both deals.

Rivals

Regulatory concerns have been one of the main planks in the P&O board's case against the Carnival merger.

P&O chiefs warned that a merger between two giants in the cruise sector would prove unacceptable to watchdogs, over monopoly fears.

The European Commission last month said it would by August complete its review into the deal.

The commission denied a request for UK watchdogs to handle the investigation, stating that the tie-up would affect a number of other European countries.

Outside Britain, the two companies are direct competitors, for instance, in Germany, where Carnival operates through Costa, and P&O owns Seetours.