BRATISLAVA (Reuters) - Slovak police have asked parliament for permission to arrest the former head of the state secret service Ivan Lexa, who is now an opposition deputy, top police officials said. Lexa, a close ally of former premier Vladimír Mečiar, is wanted for questioning over the 1995 kidnapping of the son of one of Mečiar`s most prominent critics, former President Michal Kováč and for other alleged absues of power. Lexa was not available for comment but has denied any wrongdoing. Parliament has already been asked to lift his immunity from prosecution as a deputy but officials said they were concerned he may try to interefere with the investigation. Even after a deputy`s immunity is lifted he is still immune from arrest until found guilty at trial. "There is a suspicion... that Lexa, if he were let free during the prosecution period, could mar the investigation for example by influencing witnesses," the interior ministry`s chief investigator Jaroslav Ivor told a news conference. Two other high ranking former secret service officers have already been arrested. The new reform minded government, which came to power following elections in September, has pledged to clean up Slovak society and reinvigorate the country`s democratic system. Slovakia was excluded from the first wave of European Union candidate countries because of serious concerns that Mečiar`s government was compromising democratic principles, failing to respect the rule of law and abusing the security services for political or generally illegal purposes. In February, parliament lifted the immunity of former interior minister Gustáv Krajči, opening the way for his own prosecution over a 1997 referendum on presidential elections which he is alleged to have thwarted. Both Lexa and Krajči became deputies after Mečiar`s party was defeated at last September`s elections. Mečiar had previously used extraordinary amnesty powers to try to prevent prosecutions in either the referendum or the kidnapping cases.