The last of the activists who have spent the night on the roof of a nuclear power plant have been arrested after ending their protest.

Seven campaigners braved wind and rain overnight on the roof of a building at Sizewell B in Suffolk to protest against alleged secret government plans for further nuclear power stations.

Another 44 protestors from campaign group Greenpeace who entered the site on Monday were arrested on the same day and released on police bail.

Greenpeace spokeswoman Emma Gibson said: "The weather has become so bad that the radiation monitoring equipment became waterlogged and we were worried we couldn't ensure their safety."

Activists recorded their entry into Sizewell B

The occupation of the site began at about 0630 BST on Monday.

A spokeswoman for Greenpeace said nearly 120 protesters - some wearing Homer Simpson and Tony Blair masks - broke into the coastal plant by placing ladders against the fence and climbing over.

About 50 made their way onto the roof of a cooling water pump house where they unfurled banners.

Police said at about 1830 BST on Monday, 40 protesters came down and were arrested.

Four protesters were arrested earlier in the day.

Officers from Suffolk Police monitored the protestors overnight.

In the early hours of Tuesday morning one rooftop protestor, Blake Lee-Harwood, 40, said the remaining seven had not been challenged by the authorities to come down.

"They are not making any attempt to interfere with us.

"We have tents and sleeping bags, food and water.

"We are very happy just staying here.

But by midday on Tuesday, they decided they had made their point and descended voluntarily.

If we had been determined terrorists we really could have done some damage

Greenpeace activist

Greenpeace said the protest had highlighted "pitiful" security at the plant.

A spokeswoman said: "To be honest I was quite shocked at the ease with which we got in.

"Security seemed fundamentally inadequate. It was a really pitiful level of security.

"Just two or three guards who didn't seem to know what to do."

She added: "All we were armed with was Homer Simpson and Tony Blair masks and a few banners.

"But if we had been determined terrorists we really could have done some damage."

Activists painted graffitti on the wall

British Energy, which runs the plant, disputed Greenpeace's claims on security and said the protest had created no significant dangers.

A spokeswoman said: "The protesters have not threatened staff, equipment or plant, or got close to any radiologically controlled areas or the site control room.

"They have not entered any buildings either.

"Security and safety remains our top priority."

The protest marks the first time Greenpeace has occupied a nuclear plant.

A spokeswoman would not say whether the group planned further similar protests elsewhere.

British Energy operates eight of the most modern nuclear reactor power stations in the UK, including Sizewell B, and is the UK's largest generator, producing one fifth of the country's electricity.