Caroline Flint says she is "angry and disappointed'
Former Europe Minister Caroline Flint has launched a blistering attack on Gordon Brown for treating women ministers as "female window dressing".
Ms Flint is angry that she stood by Mr Brown but he failed to promote her to full cabinet minister status.
She accused Mr Brown of running a "two-tier" government with an "inner" cabinet circle.
She is being replaced by ex-MEP Glenys Kinnock, wife of former Labour leader Neil Kinnock, who will enter the Lords.
But Labour's deputy leader, and minister for women and equality, Harriet Harman said it was untrue that Mr Brown "doesn't take women in politics seriously".
In her resignation letter, Ms Flint, MP for Don Valley, says she is "extremely disappointed at your failure to have an inclusive government".
She adds: "You have a two-tier government. Your inner circle and then the remainder of cabinet."
Ms Flint, a close friend and ally of Hazel Blears - who resigned as communities and local government secretary on Wednesday - goes on: "Several of the women attending cabinet - myself included - have been treated by you as little more than female window dressing.
"I am not willing to attend cabinet in a peripheral capacity any longer."
The criticism comes a day after Ms Flint praised the prime minister's achievements.
Equality minister Harriet Harman rejects Caroline Flint's claims over Gordon Brown
She had been widely expected to follow Ms Blears' example and resign as soon as polls closed for England's local elections on Thursday night.
But instead Ms Flint said: "I am staying in the government.
"I have spent my entire ministerial career for six years now serving Tony Blair and Gordon Brown, and I am very proud to be in a Labour government and very proud to be part of Gordon Brown's government."
Following Ms Flint's change of tone, Ms Harman said her colleague's "frustration has clearly boiled over".
But she added: "I don't accept that Gordon doesn't take women in politics seriously - not at all.
"It's certainly true to say that we have further to go.
"But as far as the reshuffle is concerned I think Gordon has got around him a good, strong team who will be focused on the issues that the voters are concerned about which is cleaning up politics, giving parliament a clean bill of health and above all putting the economy back on a course to growth."
Here is the full text of Ms Flint's resignation letter:
I believe the achievements of the Labour Government to date have been monumental and you have played an immense part in the creation of those achievements.
However, I am extremely disappointed at your failure to have an inclusive Government.
You have a two tier Government. Your inner circle and then the remainder of Cabinet.
I have the greatest respect for the women who have served as full members of Cabinet and for those who attend as and when required.
However, few are allowed into your inner circle.
Several of the women attending Cabinet - myself included - have been treated by you as little more than female window dressing.
I am not willing to attend Cabinet in a peripheral capacity any longer.
In my current role, you advised that I would attend Cabinet when Europe was on the agenda. I have only been invited once since October and not to a single political Cabinet - not even the one held a few weeks before the European elections.
Having worked hard during this campaign, I would not have been party to any plan to undermine you or the Labour Party in the run up to 4 June.
So I was extremely angry and disappointed to see newspapers briefed with invented stories of my involvement in a "Pugin Room plot".
Time and time again I have stepped before the cameras to sincerely defend your reputation in the interests of the Labour Party and the Government as a whole.
I am a natural party loyalist. Yet you have strained every sinew of that loyalty.
It has been apparent for some time that you do not see me playing a more influential role in the Government.
Therefore, I have respectfully declined your offer to continue in the Government as Minister for Europe attending Cabinet.
I served six years as a backbencher and, therefore, I am not unhappy to be able to devote myself to promoting my constituency's interests and to support the Labour Government from the backbenches.
This is a personal decision, which I have not discussed with colleagues.
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