More than three years after the national minimum wage was introduced, some employers are still refusing to pay up, a government report has found.

Enforcement system is working well when workers are not receiving the pay they deserve

Employment Relations Minister Alan Johnson

The Department of Trade and Industry said the Inland Revenue's enforcement officers had so far discovered more than �10m of wages unpaid by employers since April1999.

In the year to April 2002, �5m in wage arrears was identified.

Workers in the North West were mostly likely to be missing out. About �2.14m had been underpaid in this region, enforcers found.

The government is launching a four-week press campaign to coincide with new minimum wage rates coming into effect in October.

Whistleblowers

Average arrears identified per worker were much higher in 2002 at �495, compared to �418 in the year to April 2001 and �205 in the first year of the wage's introduction.

Unpaid wages by region

East: �349,000 South West: �138,000 South Yorkshire: �507,000 North West: �2,144,000 North East: �197,000 West Midlands: �291,000 Wales: �169,000 South East: �290,000 London: �425,000 Northern Ireland: �304,000 Scotland: �322,000 Source: Arrears of pay identified, by Inland Revenue region

As many as 36% of employers investigated were found not to be paying the minimum wage.

This represents a 6% increase on 2001/2002 and a 16% increase on 1999 to 2000.

The government said these figures indicated that the enforcement procedures were working well.

Alan Johnson, employment relations minister, said he was delighted that the vast majority of employers were now complying with the minimum wage.

"Awareness of the minimum wage is high and the enforcement system is working well when workers are not receiving the pay they deserve.

"But success has not made us complacent. Substantial extra funds are going into enforcement."

Wage explained

Workers will be encouraged to ring the minimum wage helpline on 0845 6000 678 if they believe they are being underpaid.

The minimum wage must be paid to most workers who are 18 and over and who work in the UK or normally do their work in the UK.

From 1 October 2002, the main rate for workers aged 22 and over will be increased to �4.20 an hour, and the rate for younger workers aged 18-21 will increase to �3.60 an hour.

It is a legal right to be paid the minimum wage, and workers cannot be sacked or victimised if they complain.