Spanish state vessels illegally entered the disputed waters around Gibraltar 178 times in the last 12 months, prompting a flurry of formal complaints to the Madrid government in a sign of the increased tensions over the sovereignty of the British Overseas Territory.
Of the 42 formal written complaints to the Spanish Ministry of Foreign Affairs since 2008, half were submitted in the last 12 months and the issue has also been raised directly with ministers and officials.
Figures released following Freedom of Information (FoI) requests by the Press Association show the number of unlawful incursions into British Gibraltar waters between November 2011 and the end of October this year was far higher than in previous years, coinciding with a dispute over fishing rights in the region.
Tory MP Andrew Rosindell, chairman of the all-party parliamentary group for the Overseas Territories, said it was time for the Government to step up the Royal Navy's presence in the waters around Gibraltar and to adopt a more assertive stance with the Spanish.
He said: "These figures show it is a growing problem. The Spanish are getting bolder and bolder in entering British sovereign waters. It's another way for them to try to assert their sovereignty claim, which obviously we completely oppose and challenge. They have now pushed their luck a bit too far. We need to show them we are not prepared to tolerate even the smallest of incursions."
The Ministry of Defence (MoD) said the Royal Navy responded to 178 incursions between 1 November, 2011 and October 31, 2012 but only 23 in 2011, 67 in 2010 and 26 in 2009. In July alone this year there were 40 incidents, a rate of more than one a day.
The Spanish have shown no signs of relenting in their tactics. It was reported earlier this month that the Spanish corvette Vencedora had entered British waters, leading to a showdown with the far smaller and lightly armed Royal Navy patrol boat HMS Scimitar, one of two such vessels which form the core of the Gibraltar squadron.
There were two further incidents last week, which resulted in the Spanish ambassador Federico Trillo being summoned to the Foreign Office for a dressing down.
Mr Rosindell said: "The people of Gibraltar feel like they are basically under threat. If we let the Spanish get away with it they will carry on. The time now has arrived for the British Government to come down very firmly on them. The Royal Navy needs to be there in force."
Setting out the diplomatic response to the incidents, the Foreign Office said that "in many of our written protests we raise multiple incursion incidents" but that the issue was also raised with the Spanish through other means. Its response said: "Over the course of both the last 12 months and the last five years we have, in addition to our formal written protests, raised the issue of unlawful maritime incursions in diplomatic contacts with both ministers and senior officials of the Spanish Ministry of Foreign Affairs as appropriate."