Democrat Party leader Abhisit Vejjajiva, seen here at a July event celebrating the party's founding by Khuang Aphaiwong, has embraced the new system of primary voting. (File photo by Pawat Laopaisarntaksin)

Democrat leader Abhisit Vejjajiva has insisted it is not easy for "outside elements" to try and weaken the party by nominating their own people to compete for the Democrat leadership through the primary voting system.

The Democrats will conduct a thorough background check of registered members eligible to vote for leader candidates, Mr Abhisit said Monday in response to the party's plan to introduce primary voting to select candidates vying for the party's top seat.

Mr Abhisit said checks on members are one way of keeping out any leader candidates controlled by elements outside of the party which want to exert their dominance over the Democrats.

He also urged people who genuinely share the Democrats' ideology and wish to compete for the party leadership to enter the race. If there are many such candidates, there will be less room for "controlled" leader candidates to join the competition.

Primary voting for the Democrat leadership is opened to qualified people both in and outside the party. Registered members will vote to choose the leader candidates. Candidates' names will be put up for election by the party's general meeting of executives.

Democrat executives traditionally select party leaders with members having no concrete role in picking candidates.

Mr Abhisit explained that democracy starts at home and it is important to let members participate in the process of sounding out who should stand in leadership races.

But the open process also means elements outside of the party could send their nominees who will be voted by members in the primary to stand in the leadership contest. If elected, the "nominee" candidates would go on to lead the Democrats and put the party in jeopardy, according to a political source.

Leadership primary voting is done electronically via an application. "But if something should go wrong, we have a way of suspending it," he said.

Mr Abhisit added that the qualifications for people entering the leadership primary to become candidates will be tough. For example, a person from the inside must have the support of 20 former Democrat MPs to be admitted to primary voting. The number of supporters will double if the person is from outside the party.

Meanwhile, former Democrat list MP Watchara Phethong said certain figures in the regime may be trying to get someone to give Mr Abhisit a run for his money.

He said Mr Abhisit may be viewed as an obstacle in the regime prolonging its grip on power after the next poll.

Even without Mr Abhisit as party leader, there are other Democrat stalwarts who will not make it any less easy for the regime to hang on to power, he said.

Also Monday, Alongkorn Ponlaboot, who previously quit the Democrats to become deputy chairman of the National Reform Steering Assembly, denied he was the regime's nominee and had set out to unseat Mr Abhisit.

On Sunday, he said he was approached to run for the party leadership by some former MPs and admitted he is considering it. Other potential candidates to lead the party are deputy leader Jurin Laksanavisit and ex-MP Warong Dechgitvigrom, a key rice-pledging scheme whistleblower.