BANGKOK - Thai ruling Democrat Party members still have strong confidence in Prime Minister Abhisit Vejjajiva, but it is not known if he will return as party leader, the party's spokesman Buranat Samutarak said on Monday.

Buranat said despite the election upset the Democrat Party will continue to perform its duties with full responsibility to the people.

Abhisit announced on Monday his resignation as the Democrat Party leader after the general election results on Sunday indicated that the opposition Pheu Thai Party would win.

According to party regulations, since Abhisit has resigned as party leader, all 18 members of the executive committee have also lost their party posts.

Abhisit will hold the post of caretaker party leader until the party holds a general assembly to elect a new executive committee within 90 days. No date has been fixed, the spokesman said.

Buranat said the party still had strong confidence in Abhisit's leadership. He said party members in the provinces were shocked by the news of Mr Abhisit's resignation.  Although they knew he would show responsibility, they did not expect he would do this so abruptly.

Apirak Kosayodhin, who had been tipped as a possible successor to Abhisit, declined to comment when asked whether he would accept nomination for the job. He said he would rather leave it to the party to decide.

Abhisit said Monday he has already tendered his resignation letter to the party and he would take responsibility for the results of July 3 election which saw his party lost to Pheu Thai party.

"When the party gains less voters and less seats in the House, I think a good leader needs to show spirit. Therefore, I decided to resign as the party leader today (Monday)" Abhisit said Monday morning.

The Election Commission said on Monday that the Pheu Thai Party got 265 seats of 500-seat parliament in Sunday's general election, with the Democrat Party with 159 seats.

Abhisit was elected as the Democrats leader in 2005 and has stayed in the position since. Abhisit is the 27th premier of Thailand when he came to power in December 2008 via the parliamentary agreement. He officially announced the House dissolution on May 9, half a year before the end of his office term, to call for the second election after the 2006 coup.