The nuclear safety watchdog has blocked the launch of the Royal Navy's newest reactor-driven submarine because of a risk that a dockside could collapse.

The Office for Nuclear Regulation (ONR) has barred the launch of HMS Artful, the third of Britain's Astute-class hunter-killer submarines, because of doubts about the structural integrity of the wet dock quay at Barrow-in-Furness, Cumbria.

The submarine's manufacturer, BAE Systems, had previously planned for a launch this year but now says it will be early next year. It said the problem with the dock would not cause further delays.

ONR raised its concerns in its quarterly report on the Barrow shipyard covering April to June 2013. It has ordered BAE Systems, as the site licensee, to investigate and report back on whether the dock was safe to use. "ONR placed a hold point on the launch of the next Astute-class submarine which will only be removed once the licensee can address and justify the continued use of the aging wet dock quay," the report says.

According to ONR, the quay is used to help commission the Astute-class submarines. "Recent surveys have indicated that there may be some deterioration in its structure," said an ONR spokeswoman. "As a result, the safety justification for use of this facility is being reviewed by BAE Systems to ensure that it remains valid. Until BAE Systems' investigations have been completed, ONR cannot say whether there will need to be a major programme of work. However, in the interim, ONR has placed a hold on launch of the next submarine so that we will have to be satisfied that the structure remains fit for purpose."

In a report about a visit to the Barrow yard by the Duke and Duchess of Cambridge in April, BAE Systems said Artful was due for launch this year. The first two submarines in the much-delayed £9.75bn fleet, HMS Astute and HMS Ambush, are at sea and another four are still being built.

A spokesperson for BAE Systems said: "We do not expect this to delay the launch of the next Astute-class submarine, which is scheduled for early next year. As always, if any work is required to the wet dock quay, safety will be a priority."

Peter Burt, of the Nuclear Information Service, which monitors military activities, pointed out that much of Britain's nuclear infrastructure was decades old. "It's showing its age," he said. "Hundreds of millions of pounds are being spent in secret each year as the Ministry of Defence struggles to bring ageing facilities up to modern safety standards, adding even more to the already enormous costs of the Trident replacement and Astute submarine programmes."