The Ministry of Defence (MoD) relies on fishermen and social media to alert it to foreign military activity off Scotland, the SNP has claimed.
In a speech hosted by the Royal United Services Institute, Moray MP Angus Robertson said the scrapping of Nimrod had left gaps in the UK's defence.
The RAF flew the surveillance aircraft on maritime patrols until 2011.
The MoD said maritime surveillance was provided in a number of ways, including ships and submarines.
Mr Robertson gave his speech ahead of the publication of the Strategic Defence and Security Review.
He said the review, which will be released later this year, did not take northern regional security seriously enough.
The MP said: "The Royal Navy bases all of its ocean going patrol vessels on the south coast of England and has repeatedly had gaps in their cover for UK waters.
"In recent years we have seen increasing foreign military operations close to UK territorial waters and airspace, and the UK armed forces have been known to rely on intelligence from Scottish fishing vessels and social media as they have not had the appropriate assets in place in time."
Mr Robertson said a permanent maritime patrol base should be established on the Clyde.
Jets from RAF Lossiemouth in Moray have been scrambled several times in recent months to intercept Russian military aircraft flying in the UK's so-called "area of interest".
The MoD said the military has the ability to monitor for activity off the UK.
A spokesman said: "The MoD provides maritime surveillance in a number of ways, including with surface ships, submarines, and aircraft.
"Earlier this year we announced a new helicopter-borne surveillance system to protect the future Queen Elizabeth aircraft carriers.
"We continue to assess future requirements and options as part of the work we are doing on the Strategic Defence and Security Review."