MILLIONS of children's Christmas presents could be stranded at sea after tug workers threatened to go on strike and block Southampton docks.

Unions today warned tug workers were planning a strike ballot after a dispute with bosses Adsteam.

A blockade of Southampton docks, which handles most of the UK's trade with the far east, could see Christmas favourites such as games consoles, TVs and i-pods stuck at sea rather than under the Christmas tree.

Union bosses claim strike action by tug workers could mean bring all UK ports, including Southampton, to a standstill and see empty shops on the high street within five days of the action starting.

As well as dealing with seven per cent of all UK trade, Southampton is Britain's biggest vehicle handling port with 740,000 cars passing through every year.

If the port was blocked it could leave thousands of valuable vehicles afloat.

The knock-on effects of any action would be vast with more than 12,000 regional jobs relying on port activities.

A Transport and General Workers Union spokesman estimated between and 30 and 40 Southampton tug workers could shortly be voting on whether to strike.

The row between staff and Australian owned tug firm Adsteam centres on a complex issue about staff registration.

Workers are unhappy at having their registration switched from the UK to Guernsey three years ago.

Graham Stevenson, national organiser for transport for the TGWU, said: "Ships are getting bigger and bigger and big ships can't visit Britain without the tug.

"If they don't pull the ships in then the ships don't come and if the ships don't come Britain shuts down in five days.

"The core problem is that we want to renegotiate the registry of workers back to the UK and Adsteam is being unhelpful about it.

"There is a real strength of feeling and people are very motivated by this. It's very clear."

Adsteam's Chief Executive Europe, Stephen Eastwood said: "Adsteam have been considering for some time the return of employees from Guernsey to the UK.

"The transfer back to the UK has some potential complications in terms of employment contracts, which need to be resolved.

"In principle the company has no objection to the change because it would have no benefit or detriment to either Company or employees.

"Adsteam has not received any formal notice from the Union regarding its intention to ballot its members in accordance with UK employment legislation. The formal process will take several weeks during which a solution can be sought."

Harbourmaster and deputy port director Captain Stephen Young said: " Obviously it's out of our control but we hope they resolve the issue. We hope that dialogue continues and there's a satisfactory resolution."

Southampton Container Terminals, which has its busiest period as retailers rush to cope with the demand in the run-up to Christmas, declined to comment.