New Delhi, Dec 15: The nationwide postal strike continued to disrupt services for the 11th day today even as the Centre, which has declared it illegal, asked the state governments to take stern action including invoking of Essential Services Maintenance Act (ESMA) if the situation so warranted.According to official sources here, the Centre has written to six states including Karnataka, Madhya Pradesh, Delhi and Haryana where the state laws provided for invoking ESMA.The Government had on Thursday declared the strike as "illegal" and repeatedly asked the six lakh employees to return to work, but they remained unrelenting in their stand that the stir could be ended only if the demand for implementation of the the Justice Talwar committee report on wage revision and other benefits were met."The unions have decided to be firm and the strike will not be withdrawn until all the demands are met," G K Padmanabhan, secretary general, Federation of National Postal Organisations told PTI.The strike had its echo in Parlament and opposition CPI(M) and RJD members walked out of Lok Sabha dissatisfied with the reply by Communication Minister Ram Vilas Paswan on their calling attention motion over the strike.Paswan said "the Delhi High court has directed that postal services be restored by December 15 and that it shall be open to the Government to take such steps as are warranted for restoration of postal services, including resort to ESMA if the situation so warranted.In the Rajya Sabha where opposition members charged the government with being "apathetic" towards the suffering of employees, described the Delhi High Court's order as "erosion of power of executive".Members, cutting across party lines, said while the strike had no doubt caused inconvenience to people, at the same time the government should ensure that the just demand of the employees should also be taken into consideration.Meanwhile, apprehending law and order problems in the aftermath of the strike being declared "illegal", the cabinet secretary wrote to the Chief secretaries of the state asking them to take appropriate measures to maintain law and order on the postal front.The Department of Posts (DoP) has issued instructions to all postal circles to ensure essential postal services.While the government sought to utilise the services of retired employees of the department, students, NCC and non-government organisations for maintaining the service, the unions maintained that the strike was "near total".