Former Defence Secretary Lord Browne has warned that the UK nuclear weapons system could be rendered obsolete by cyber attacks.
The ex-Labour minister told the BBC unless “weak spots” were protected, there was “no guarantee” of a reliable nuclear deterrent for the PM “when he needs to reach for it”.
Ex-Conservative Defence Secretary Sir Malcolm Rifkind played down the risk.
The comments come ahead of a Commons debate on the future of Trident.
On Monday it was revealed the cost of renewing the system had risen to £31bn.
The government also said the start date for the replacement submarines had been put back until “the early 2030s” as it unveiled its Strategic Defence and Security Review (SDSR).