Andy Goss, PCGB managing director, said: “The reduction is designed to enable customers to buy in this country with renewed confidence.”
Other companies have announced price cuts or are considering their position following the release of the Competition Commission report.
Alfa Romeo last month announced a “range restructure” which was the first major response to Trade and Industry Secretary of State Stephen Byers' call for lower new car prices. Like Porsche, Alfa Romeo has been affected by unofficial imports, especially on the 156.
Alfa Romeo prices are, on average, being reduced by 15%, with a further “customer benefit” of almost 5% through higher specifications.
A spokesman for BMW GB - poised to announce cuts, according to industry speculation - denied Porsche's announcement would influence its decision.
“Consumers are expecting a cut of 10-12% and we must make a judgement on our policy,” he said.
Porsche's prices now range from the basic Boxster at £31,450 (down £2,782) to the 911 Turbo at £86,000 (down £8,749).
The 911 entry price (for the Carrera coupe) is £55,950, a £4,321 cut from last month's £60,271. The 1995 price was £56,495.