LUXEMBOURG, Oct 25 (Reuter) - European Fisheries Commissioner Emma Bonino faces defeat on Thursday over rules to control fishing in Western waters, EU diplomats said.

The new rules are due to take effect on January 1 next year when Spanish and Portuguese fishermen are allowed into fishing grounds off the west coasts of Britain and Ireland.

"It's the last major piece of the jigsaw," one diplomat said before a meeting of EU fisheries ministers.

Last December fisheries ministers agreed to allow 40 Spanish vessels into most of the "Irish box", a fiercely protected fisheries zone around Ireland.

In June, they decided how many Spanish vessels could fish in the northern and southern parts of the box and fixed fishing limits, based on engine capacity and days spent in fishing zones.

Bonino's proposal that all EU fishing vessels must report each time they enter and leave port and from fishing zones met fierce resistance from Britain and other countries as being too bureaucratic and cumbersome.

The Spanish EU presidency has put forward a compromise,backed by the main fishing countries -- Britain, Ireland, France, Portugal and Spain -- of less stringent reporting requirements.

A unanimous decision would be needed by the 15 member states to overrule the European Commission.

Commission Fisheries Spokesman Filippo di Robilant said the presidency's plan was unacceptable because more relaxed controls would put fish stocks at risk.

"It's not too difficult or too costly to make a radio call. kippers are on the air all the time," he told Reuters.

The Commission says it will be difficult to control fishing, especially by Spanish and French vessels, which will be able to register in British and Irish ports and land catches there.

It insists that reporting is needed to reinforce traditional controls, such as total allowable catches and quotas.