Andrew Flintoff will retire from Test cricket at the end of this summer's Ashes series. The England all-rounder has confirmed the news after admitting that his injury problems have got the better of him.

"My body has told me it's time to stop," Flintoff said. "It's been something I've been thinking about for a while and I think this last problem I've had with my knee has confirmed to me that the time is now right."

Flintoff, who has missed 25 of England's past 48 Tests, is yet to prove his fitness for the Lord's Test against Australia that starts tomorrow, having aggravated a knee injury during the first match of this summer's series at Cardiff.

However, Flintoff remains optimistic of being fit to face Australia at Lord's after undergoing fitness tests today.

"Excuse the pun, but [deciding to retire] is not a knee-jerk reaction," he said. "it's something I've been thinking about for a while. It's just the timing of it. I think with this latest thing with my knee, seeing the surgeon Monday and having jabs in it, my body is telling me it's time to give in.

"For my own sanity I can't keep going through rehabilitation, I think I've done two years in the past four, just rehab all the way through.

"I've got four Test matches, and I'll give my utmost for England to try and contribute to an Ashes win, so that's what I'm focusing on over the next few weeks.

"I've bowled a few overs this morning, but we'll make the final decision in the morning, just to check everything is fine, and have another bowl before they announce the final team, but I'm very hopeful at this stage.

"For the next four Test matches I'll do everything I need to do to get on a cricket field and I'm desperate to make my mark," Flintoff added. "I want to finish playing for England on a high and if you look at the fixtures going forward, the way my body is suggests I won't be able to get through that.

The 31-year-old has struggled with injury throughout his career and it is thought that his decision to call time on his Test career is an attempt to prolong his participation in 50-over and Twenty20 international matches.

Flintoff has undergone four ankle operations as well as suffering back, hip, shoulder and groin problems and has come to the decision after expressing doubts that his body can cope with the physical demands of Test cricket.

"It's been a hard decision but a decision that's been pretty much made for me," he said. "All the rehab and injuries I've had over the last few years take their toll on you. My body's telling me things and I'm starting to listen.

"I've still got the chance to play international cricket - I'm going to carry on playing one-day internationals and Twenty20s. I'm hopefully going to be a big part of English cricket still.

"It's also important for the team that I make this announcement because they need to move on. They can't keep waiting for me to get fit or for me to play a game here and there - they need to give someone else a chance to make their way in the game.

With his decision now public, Flintoff said he was focused on enjoying the remainder of the series.

"Now it's out there it's almost a burden off my mind and I can get on with playing Test cricket and enjoying it for four more Test matches," he said.

"There's only pressure that you put on yourself. Going into an Ashes series on a lot of players there is a certain amount of pressure. I said before this series it's something I'm going to relish."

The Lancashire all-rounder, who has played for England 75 times over 11 years, is reported to have told his team-mates of his decision before today's practice session at Lord's. Flintoff has taken 212 wickets and scored 3,658 runs including five centuries during his Test career.