The boycott by the opposition has raised the possibility of by-elections and is a setback to Erdogan [AFP]

Two of Turkey's principal opposition parties have boycotted parliament's swearing-in to protest against a ban on jailed candidates who won seats in June's parliamentary elections.

The decisions by the secularist, centre-left Republican People's Party (CHP) and the pro-Kurdish Peace and Democracy Party (BDP) meant that more than 30 per cent of candidates elected abstained from Tuesday's ceremony.

"We will not take the oath unless the way is open for all our deputies to take the oath," Kemal Kilicdaroglu, the CHP leader, said earlier in the day.

The CHP, which won 135 seats in the 550-seat legislature in the June 12 election, took its decision after a court rejected an appeal for the release of two of its victorious candidates.

"These people received the support of the people, and people expressed their will on behalf of these two deputies, and I think our action is designed to make sure that the right to elect and to be elected is fully respected," Faruk Logoglu, a CHP member, told Al Jazeera.

"We understand that this action is not going to produce the desired outcome until the governing majority party comes up with a solution that is acceptable."

'Lame' institution

Logoglu said that while the parliament would still be able to function, as the ruling AK Party holds a majority, it would do so as a "lame" institution.

The BDP, which won 36 seats, announced its bycott decision last week after the Election Commission ruled a candidate must forfeit his seat because of a conviction for spreading "terrorist propaganda" and awarded the seat to a runner-up from the AK Party.

The boycott has raised the possibility of by-elections and is a setback to Recep Tayyip Erdogan, the Turkish prime minister.

Read more about the Turkish elections 2011

There is a rule that if more than five per cent of MPs resign, their seats will be thrown open for by-elections.

However, the fact that candidates cannot resign unless they have been sworn-in, leaves the issue in a grey area.

Erdogan, who heads the AK Party, has pledged to build bridges and seek consensus with the opposition as he prepares to draft a new constitution to replace one written during military rule.

The opposition parties argue that the jailed politicians are entitled to parliamentary immunity and should be freed to take up their seats in the house.

They have also called on Erdogan to amend the necessary laws to facilitate the release of detained candidates.

But Erdogan has indicated his party had no immediate plans for an amendment, saying the problem would be solved later with a more democratic constitution.

He criticised the opposition parties for nominating jailed candidates late on Monday, saying: "Could they not have found other candidates? They nominated these people knowing that it would cause such a problem."

Source: Al Jazeera and agencies