The UK's second largest insurer Prudential has revealed it will write to customers telling them they have just six months left until the final date by which they can make a complaint about being mis-sold an endowment mortgage.

Under current FSA rules, customers have three years to lodge a complaint from the date they receive their first ‘red’ letter indicating that there is a high risk their mortgage endowment may not achieve its projected final value.

Therefore, Prudential and Scottish Amicable customers who received their first red letter three or more years ago will have six months from the date of the letter advising them of the introduction of the complaint deadline in which to make a complaint if they felt they were mis-sold. Prudential says almost all of the 110,000 customers being contacted fall within this category.

If customers received their first ‘red’ letter less than three years ago, the effective date of their deadline will be three years from the date of their original ‘red’ letter or six months from the date of the letter advising them of the introduction of the complaint deadline – whichever is the later.

Prudential has approximately 216,000 mortgage endowment policies in force. It stopped selling mortgage endowment policies in January 2001. Meanwhile, Scottish Amicable has approximately 501,000 plans in force but withdrew from the mortgage endowment market in April 2001.