PA MediaJoani Reid stepped down from the Labour Party last monthA senior naval officer was investigated last year over allegations of an inappropriate relationship with Scottish MP Joani Reid, BBC News understands.
The East Kilbride and Strathaven MP stepped down from the Labour Party last month after her husband was arrested on suspicion of spying for China.
At the time, Reid released a statement saying she was not under investigation by the police and she had done nothing wrong.
It is understood the naval officer - who commanded a nuclear-armed submarine based at Faslane - was not subject to any disciplinary action following the allegations about the relationship with Reid and was not found to have broken military rules.
PA MediaFaslane is the base for the UK's nuclear submarinesAs first reported in the Financial Times, security checks were also carried out following the allegations and the Ministry of Defence was understood to have been satisfied.
The officer is no longer in charge of a nuclear submarine. This is understood to be unrelated to the investigation, and he is still in the Navy.
The Faslane naval base on the Gare Loch, about 25 miles (40km) north-west of Glasgow, is the home of all the Royal Navy's nuclear submarines.
This includes the UK's four Vanguard-class ballistic missile submarines which carry Trident nuclear missiles.
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A Royal Navy spokesperson said: "The security of the nuclear deterrent is our highest priority, and we have robust processes in place to protect the security of our people and capabilities.
"We will not comment on individual cases."
BBC News has approached Reid for comment.
Her husband, David Taylor, was one of three political advisers who were released on bail after being accused of assisting a foreign intelligence service last month.
Reid voluntarily suspended herself from the Labour Party while an internal investigation was carried out, and is now sitting as an independent in the House of Commons.
Royal NavyScotlandLabour Party
