(Adds explusion of corruption probe prosecutors)
By Daren Butler
ISTANBUL, May 12 (Reuters) - A top figure in Turkey's AK Party said trust in the judiciary had been eroded during its time in office, comments likely to anger President Tayyip Erdogan and pointing to unease in the ruling party ahead of a parliamentary election.
Deputy Prime Minister Bulent Arinc, a rare senior voice of dissent in the party in the past, suggested in a television interview that the Justice and Development (AK) Party had lived up to only half its name over more than a decade in power.
"What I am sad about is that we are very good on development, but are we so good on justice?" Arinc, who has served the maximum three terms in parliament and is not standing in the June 7 election, told Haberturk TV late on Monday.
"We have made very nice palaces but we have to work hard to increase confidence in justice and the judiciary," he said, referring to "palaces of justice", the new courthouses built under the AKP, which was founded by Erdogan.
Domestic and foreign critics accuse Erdogan of undermining the judiciary as a counterweight to his growing power.
Some senior party officials have privately expressed unease over Erdogan's continued interference in government affairs since assuming the presidency - which in its current form is constitutionally largely a non-executive post - and suggested it is chipping away at AK Party support ahead of the June vote.
While Arinc's latest comments did not target the president directly, they follow judicial reforms under Erdogan to purge the influence of an Islamic cleric whom he accuses of trying to topple him with a manufactured graft scandal.
Hundreds of judges and prosecutors and thousands of police officers have been purged or reassigned since the corruption investigation targeting Erdogan's inner circle emerged in late 2013. Related court cases have since been dropped.
Erdogan says the scandal was contrived by U.S.-based cleric Fethullah Gulen, a former close ally who denies the accusation.
The High Board of Judges and Prosecutors expelled from their profession four prosecutors and a judge associated with the graft cases, saying they had tarnished the profession's honour.
Opinion polls point, for all the controversy, to a clear AKP victory in June; but it may fall short of the strong majority Erdogan wants to anchor his power with a full presidential system, something the AKP sees as a priority.
In February, Turkey's outgoing top judge warned that the judiciary could become an "instrument of revenge" in the hands of political authorities, after government-backed candidates strengthened their grip on key courts.
"If the trust felt for the judiciary has fallen to around 20 percent in a country ... we should put our heads between our hands and think hard," Arinc said. (Editing by Nick Tattersall and Ralph Boulton)