Lawmakers from the ruling UMNO closed ranks behind Malaysia's prime minister on Tuesday, while the son of former premier Mahathir Mohamad also ignored his calls for members to follow him in leaving the party.

Mahathir had resigned from the party on Monday in an attempt to force his handpicked successor to quit, saying he would not return to the United Malays National Organisation (UMNO) until Prime Minister Abdullah Ahmad Badawi left office.

Mahathir's move sparked talk of mass resignations from UMNO by his supporters and fears of political turmoil, but Malaysia's domestic trade minister said after a special meeting between MPs and the premier that no party members were resigning.

'Nobody is moving out of UMNO... none of us is leaving UMNO,' said Shahrir Samad, after the meeting attended by 73 out of 79 UMNO lawmakers.

One minister criticised Mahathir's move as blackmail.

'Nobody, no matter how big he is, can use dirty tactics to bring down somebody who is democratically elected,' said minister in the Prime Minister's office, Mohd Nazri Abdul Aziz.

'It is not something that we condone. It is blackmailing the party.'    

Abdullah declined to speak to reporters after the meeting.

UMNO members said an MP from southern Johor state, Mohamad Aziz, stood up to pledge support on behalf of fellow lawmakers for the premier, who has rejected Mahathir's call to step down.

The former premier's son, Mukhriz Mahathir, who is a lawmaker with UMNO, said later on Tuesday he will not quit the party, dealing another blow to his father's bid to oust the Prime Minister. But Mukhriz echoed his father's call for Abdullah to step down.

'I reserve my right as a voice of constructive criticism towards the present leadership,' he told reporters.

'This is my stance at the moment. I reserve to change the stance in the event circumstances warrant it. There is no compromise but he (Abdullah) resigns. I am staying back to fulfil my aspirations to do good for the party,' he said.

'At the moment, we have the weakest leader in UMNO's history.'    

Mahathir's departure came three days after Abdullah ordered the attorney-general to investigate him and five others on possible offences over the appointment of judges while Mahathir was in power.

It added to concerns about the ruling Barisan Nasional (BN) coalition's hold on power, as the emboldened opposition, headed by Mahathir's political foe, Anwar Ibrahim, has been trying to seize power from the coalition by wooing defectors after BN's poor elections showing in March. - Reuters