The Minister for Transport Paschal Donohoe has said the planned seven days of strikes at Dublin Bus and Bus Éireann next month would cause grave difficulties for both passengers and the companies themselves.

He urged trade unions representing staff in the State-owned bus companies to return to the Labour Relations Commission. He said this was the forum at which their concerns could be addressed.

The trade unions Siptu and the National Bus and Rail Union (NBRU) are to stage work stoppages on Friday May 1st; Saturday May 2nd; Friday May 15th; and Saturday May 16th as well as on Friday, Saturday and Sunday May 29th, 30th and 31st.

This would see travel disruption take place on both the May and June bank holiday weekends.

The industrial action is in protest at plans by the National Transport Authority to put out to tender 10 per cent of routes currently operated by Dublin Bus and Bus Éireann.

Unions fear their members could face a reduction in their terms and conditions of employment if they were forced to move to any private bus operators that won tenders to operate the routes.

The Minister told RTÉ Radio that it was required under legislation for the routes to be put out to tender.

He said last year the State invested €90 million in the bus companies.

The Minister said the tendering plan was aimed at generating competitive tension in the market, to deliver greater value and to provide more choice for passengers.

He argued that the bus market would increase in size in the future and that Dublin Bus and Bus Éireann would be bigger and employ more people.

The Minister said the two State-owned bus companies could compete in the tender process.

Talks which had been underway at the Labour Relations Commission over recent months onthe bus route tendering plan collapsed at the end of March.