* Cameron had doggedly defended scandal-hit minister
* But media, political pressure forced her resignation
* Cameron's judgment questioned by opponents
* Scandal hurting Cameron's party ahead of European election (Recasts, updates with Cameron, Miliband, appointments)
By Andrew Osborn
LONDON, April 9 (Reuters) - British Prime Minister David Cameron suffered a blow to his authority on Wednesday when a scandal-hit minister he had been doggedly defending resigned, exposing him to charges of weak leadership and poor judgment.
Maria Miller, Britain's minister for culture, stepped down after a backlash against her expenses claims disrupted efforts by Cameron and his ruling Conservative party to woo voters ahead of European Parliament elections next month.
Cameron's party is expected to finish a humiliating third in the European ballot behind the surging anti-EU UK Independence party (UKIP) whose leader had accused Cameron of making a "catastrophic" error of judgment by failing to sack Miller.
Conservative lawmakers had also begun to fret that the Miller imbroglio was damaging their party's image and its hopes of winning a national election in 2015.
UKIP, which has styled itself as an anti-establishment party, had seized upon the case of Miller, who gave a perfunctory 32-second public apology last week, as an example of how remote and venal the country's political elite is.
Michael Heaver, a spokesman for the party, said on Wednesday the furore had badly shown up the Conservatives, who are also known as 'Tories' in Britain.
"Entire Maria Miller affair shambolic for Tories and shames British politics," he wrote on Twitter. "Cameron and top table Tories dangerously out of touch."
UNDER PRESSURE IN PARLIAMENT
The opposition Labour Party, which is battling it out with UKIP for first place in the European elections, strongly criticised Cameron during fiery exchanges in parliament over his refusal to sack Miller.
How, it asked, could he have justified leaving her in place when a report had ordered her to pay back wrongly claimed money and found she had tried to hinder an inquiry into the matter.
"He still doesn't understand what she (Miller) did wrong," Ed Miliband, Labour's leader, said of Cameron.
"The reason the public were so appalled was if it had happened in any other business there would have been no question about them staying in their job. Why was he the last person in the country to realise her position was untenable?"
Cameron, who continued to say that Miller was doing an excellent job right up until her abrupt resignation, defended his handling of the scandal, pointing out that Miller had been cleared of one of the main allegations against her despite being found wanting in other areas.
"I thought it was right in those circumstances to allow her to make her apology and continue with her job. That is the way I think is the right way to handle it", he said, accusing Miliband of jumping on a political bandwagon.
Cameron appointed former banker Sajid Javid as the country's new culture minister to replace Miller.
Cameron said on Twitter that lawmaker Nicky Morgan would step up to the financial secretary post at the Treasury, while Andrea Leadsom would become the new Economic Secretary.
The decision not to replace Miller with another woman attracted immediate criticism.
Miller was one of just four women in Cameron's cabinet of 22 and Labour have long accused him of doing too little to promote women to senior jobs.
"There are now just three women running Government departments out of a possible twenty two, demonstrating that when it comes to women, it's out of sight, out of mind for this out of touch Government," Gloria De Piero, a Labour lawmaker and spokeswoman for women and equalities, said in a statement.
In her resignation letter, Miller said she felt the scandal had become a distraction from the government's work. Cameron said he was sorry to see her go, but accepted her resignation.
The issue of lawmakers' expenses is a sensitive one in Britain after reams of them were leaked to the press in 2009, exposing widespread abuse. That shook the political establishment and dented public confidence in politics.
Miller was cleared of one central allegation against her - that she used her expenses to cover her parents' living costs. But she was found to have inadvertently over-claimed mortgage costs. One inquiry put the amount Miller had over-claimed at 45,000 pounds ($75,400), another at 5,800 pounds ($9,700).
($1 = 0.5970 British Pounds) (Additional reporting by Michael Holden, Kylie MacLellan and William James; Editing by Ralph Boulton)