The Shard's viewing platform was closed on Thursday afternoon because of the six Greenpeace activists climbing up the building.
The women, who are campaigning against BP's Arctic drilling, had been scaling the skyscraper since 4am.
By early afternoon, they were 180 metres high.
In a statement, the Shard's management said: "The Shard continues to work with the emergency services and we are in constant discussion with the Greenpeace representatives to ensure the safety of the protestors.
"In the interests of public and protestor safety, the building’s emergency response team has advised The View to close with immediate effect.
"We apologise to guests for the inconvenience caused and The View will be pleased to honour their tickets either later on today or on a different date.
"All three restaurants and our offices remain open at this stage. We take security, health and safety of all our occupiers and visitors to the building extremely seriously."