Stephen Harmison's impressive performance against Australia this week has failed to earn him a place in England's squad for the first npower Ashes Test in Cardiff.

The Durham fast bowler took six wickets for England Lions during their drawn match against the touring side in Worcester, including dangerous opener Phil Hughes in both innings, but the selectors have instead included Graham Onions, his Durham team-mate, in a 13-man squad.

Onions claimed ten wickets in the one-sided series win over West Indies earlier this summer and has been added to the England line-up who drew their practice match against Warwickshire last week while Ian Bell is included as cover for the batting.

"We were delighted with the way in which the team performed in the warm-up match at Edgbaston and it was very encouraging to see Andrew Flintoff bowl so well on his return to the side," Geoff Miller, the national selector, said. "We were keen to show consistency in selection and retain the nucleus of the side that performed so well against West Indies in the Test series earlier this summer.

"Graham Onions has made an excellent start to his Test career and gives us a different option when we consider the make-up of our bowling attack and the type of conditions we will encounter."

Tim Bresnan, the Yorkshire all-rounder, has dropped out of the squad having featured for the first time against West Indies to accommodate the return of Flintoff, who has been recalled after missing the start of the season while he recovered from a knee operation.

Monty Panesar, the left-arm spinner, also returns after missing the West Indies series while both Harmison and Ryan Sidebottom, the Nottinghamshire left-arm seamer who claimed two wickets in their championship match against Lancashire this week, have been given encouraging messages by Miller at the start of the series against Australia.

"There is healthy competition for places in our starting line-up at present and the strong performance by the England Lions against Australia at Worcester demonstrated that we are starting to develop a larger squad of players who can compete effectively with international class players," Miller said.

England squad to play Australia in first npower Ashes Test: AJ Strauss (Middlesex, capt), AN Cook (Essex), RS Bopara (Essex), KP Pietersen (Hampshire), PD Collingwood (Durham), MJ Prior (Sussex, wkt), A Flintoff (Lancashire), SCJ Broad (Notinghamshire), GP Swann (Nottinghamshire), JM Anderson (Lancashire), MS Panesar (Northamptonshire), IR Bell (Warwickshire), G Onions (Durham).