The Royal Navy was criticised on Thursdayfor using a patrol vessel rather than a frigate to escort a Russian naval flotilla through the English Channel.

For the third time in two months the Russians sent their ships past the UK’s southern coast, when the spy ship Feodor Golovin, landing ship Alexander Ostrakovskiy and tanker Yelnya returned to their base ports in the Baltic and Barents seas.

The ships had been supporting Russian operations in Syria.

Accompanying them through the Channel were the Royal Navy’s patrol ship HMS Mersey and a Wildcat helicopter from RNAS Yeovilton.

But observers noted the absence of any naval frigate to shadow the Russian vessels, raising questions about the impact of spending cuts on the Navy’s ability to respond to potential threats.

Navy Lookout, an online campaign set up to “promote the Royal Navy and fight its decline”, said: “Obviously it is worrying we don’t have more frigates around UK coast for these tasks but it is a matter of responding best with assets available.”

Luke Skipper, the former chief of staff for the Scottish National Party’s Westminster Group, said: “Less than five years ago the Royal Navy specifically said they [patrol boats] were not the right vessels. I wonder what has changed?”