One-day international, Old Trafford: Sri Lanka 318-7 (50 ovs) bt England 285 by 33 runs
Sri Lanka stayed on course for a series whitewash as England faltered again to lose the fourth game by 33 runs.
Cook's maiden innings was one of few bright spots for England
Skipper Mahela Jayawardene was dropped twice early in his innings and went on to his second successive hundred.
Farveez Maharoof added an unbeaten 58 with two sixes in a total of 318-7, the highest one-day score at Old Trafford.
England needed someone to play a major innings in reply but although their top nine all reached double figures, the highest score was Andrew Strauss's 45.
In his one-day international debut, Alastair Cook helped Marcus Trescothick give England an excellent start and his sixth four took the total to 50 in the ninth over.
Trescothick survived a simple chance to keeper Kumar Sangkkara on 17 and hit eight boundaries, but after digging out a series of yorkers from Lasith Malinga, he eventually drove straight to mid-off and departed for 44.
Cook's bright innings of 39 ended in the next over, bowled by Dilhara Fernando, when an inside edge crashed into the stumps.
Strauss and Ian Bell then batted with quiet purpose, the captain bringing up the 100 in the 17th over with successive cuts for four when Maharoof dropped short.
But with his team in a useful position Strauss tried a late cut a ball from off-spinner Tillakaratne Dilshan and edged straight into keeper Kumer Sangakkara's gloves.
In the next over Bell, having played another composed innings of 30, was bizarrely dismissed when he strayed out of his ground and was stumped when the ball rebounded off Sangakkara's chin onto the bails.
Tim Bresnan hit two fours in a belligerent 20 off 13 balls to kindle faint hopes in the latter stages but schoolboy-style confusion over a third led to his run out, leaving Liam Plunkett (29) to hit a couple of big sixes before the final act occurred with England on 285.
Another much-changed home line-up saw four changes, with Cook included along with Vikram Solanki, Kabir Ali and Bresnan.
Injury doubts Kevin Pietersen and Paul Collingwood were not risked, leaving a team with 358 one-day caps between them, less than Sanath Jayasuriya's personal tally for Sri Lanka.
The first ball of the match brought excitement to England's world weary followers as Steve Harmison found sharp pace and bounce to rap Upul Tharanga on the glove.
Maharoof's cameo too Sri Lanka to a record total
But the rest of the over typified England's recent inconsistency with three wides on either side of the wicket, and the 21 in the innings took the series total to 70.
Jayawardene's first reprieve came off Harmison in the ninth over when Bell at backward square-leg failed to cling on to his hook.
Bresnan replaced Harmison to bowl the 11th over and after his first ball was launched over extra cover dismissively to the fence by Jayawardene, Jamie Dalrymple could not hold leaping at full stretch, or on the rebound.
Having ended the record stand in the 25th over when Tharanga (60) chipped Dalrymple to mid-wicket, England chose to complete the powerplays and gradually began to peg Sri Lanka back.
Sangakkara edged another hostile lifting ball from Harmison, and in the second over after a 20-minute rain delay Dilshan missed a straight one from Plunkett.
Four wickets fell for 54 inside 12 overs but Kabir's final spell saw two waist high full tosses that were hammered for four by Malinga Bandara, who then hit a mighty six over mid-wicket.
The final over saw Maharoof complete fifty from 47 balls with two hooks for six off Kabir, who then saw him caught off a no-ball.
That took the eighth-wicket partnership to 68 from the final six overs and ensured England's beleagured batsmen would have a formidable chase.
It was a task which was beyond them and they now face the task of raising their game at Headingley to deny Sri Lanka a clean sweep.