WASHINGTON — The White House insisted Friday that it broke no laws by asking ex-president Bill Clinton to find out whether a Democratic Senate candidate would quit his race if he was offered a job.

The Obama administration defended its efforts to persuade Joe Sestak not to run in Pennsylvania in a party nominating race he eventually won against incumbent Senator Arlen Specter, who left the Republicans to run as a Democrat.

"We have concluded that allegations of improper conduct rest on factual errors and lack a basis in the law," White House counsel Robert Bauer said in a memorandum (PDF) on the affair which is blowing up into a political storm.

Bauer denied reports that Sestak, a retired admiral, was offered a post as navy secretary, but said he was sounded out by Clinton on the possibility of an unpaid post if he stayed in the House of Representatives.

Bauer said Sestak was asked whether he was interested in serving on a presidential or other senior executive advisory board to avoid a "divisive Senate primary."

"Congressman Sestak declined the suggested alternatives, remaining committed to his Senate candidacy," the memo said, without specifically outling exactly which posts Sestak was offered.

Clinton was asked to discuss the situation with Sestak by White House Chief of Staff Rahm Emanuel, who worked as a senior advisor during the former president's administration.

The memo also argued that there had been "numerous, reported instances" in the past when prior administrations had discussed "alternative paths to service" for candidates considering campaigns for public office.

Republicans have demanded a special prosecutor in the case, to see whether any laws which prohibit the offer of employment in government jobs in return for political activity were broken.

Democrats have also increasingly called on Sestak to clarify exactly what transpired ahead of critical November elections, in which Democrats fear heavy losses.

Previously, the White House had insisted nothing improper happened in the episode, and President Barack Obama promised on Thursday that the administration would throw some light on the affair.

Clinton still towers over Democratic Party politics, and might be supposed to have influence with Sestak, who was a fervent supporter of Hillary Clinton during her Democratic presidential primary run against Obama.

The affair could have some political impact on Obama, who came to power promising transparency and to clean out the corrupt and insider politics for which Washington is known.