Rabat  - One of Morocco's biggest trade unions Wednesday called a general strike for May 13 amid mounting tension between the government and unions ahead of the May 1 Labour Day marches.

The Democratic Labour Confederation (CDT) said the strike would protest an absence of government response to union requests to raise salaries and to improve the purchasing power of employees in the North African kingdom where the prices of many basic products have gone up dramatically.

Four rounds of negotiations had yielded no results, the CDT complained.

The CDT announced last week that the nine representatives it had in the Moroccan senate were leaving the institution.

One of the nine, Khalid Houir Alami, said they wanted to call for a "national debate on the democratic question in Morocco, to begin with free and democratic elections and credible representative institutions."

Several other trade unions pledged to join the strike which, if it is carried out, could spark what observers described as one of the biggest waves of union protests in Morocco in the recent decades.

Two trade unions, the UMT and the FDT, on Monday rejected a government proposal to raise the minimum salary by 5 per cent. (dpa)