UPDATE 4-Climate change activists briefly block UK's Port of Dover

(adds UK seeking further powers)

LONDON, Sept 24 (Reuters) - Climate change protesters on Friday blocked the entrance and exit to the Port of Dover, Europe's busiest trucking port, after causing disruption earlier this month to Britain's busiest motorway.

About 40 activists from the environmental group Insulate Britain briefly brought to a standstill all traffic to and from the Port of Dover, which handles about 6,000 trucks a day as the main artery for trade over the English Channel.

The group has already blocked London's M25 orbital motorway five times in the last two weeks, prompting the government to take legal action.

Insulate Britain wants the government to commit to providing insulation for 29 million homes as part of efforts to curb energy consumption, and thus use of fossil fuels that are driving up global temperatures.

"The Port implemented its tried and tested resilience plans in order to deal with the impact of the protest," Doug Bannister, its chief executive, said in a statement.

Police said they had made 39 arrests and the route had been cleared.

On Tuesday, the government secured a court order against the climate change activists, which means they could face prison if they blocked the M25 again.

That action has seen protesters obstruct slip roads and the carriageway itself by gluing themselves to the road and pouring paint on it.

'RECKLESS BEHAVIOUR'

Transport minister Grant Shapps said the government would now seek to take further legal action.

"We won't tolerate reckless behaviour on motorways or ports (Dover this morning)," he said on Twitter. "I’m therefore seeking a further injunction to prevent this disruption. Living in a democracy everyone is entitled to protest, but that doesn't extend to closing roads and ruining livelihoods."

Insulate Britain says the government should fund the insulation of all social housing by 2025. Nearly 15% of the UK's total greenhouse gas emissions come from heating homes, it says.

In a statement the group apologised for the disruption it was causing but said it was "the only way to keep the issue of insulation on the agenda".

Britain, which aims to achieve net zero greenhouse gas emissions by 2050, will host the UN COP26 climate summit in Glasgow in November, where Prime Minister Boris Johnson will push world leaders to commit to ending reliance on fossil fuels.

(Reporting by Michael Holden, Editing by Giles Elgood and Gareth Jones)