A blame game is emerging over IT failures at Heathrow's £4.3bn Terminal 5, after new problems emerged at the weekend, a week on since the opening of British Airways' new hub.

New IT problems emerged on Saturday as the automated baggage 'reconciliation system' experienced what BAA called "a problem", forcing BA to sort bags manually. The system links bar-coded bags to individual passengers, and is designed to automatically control the return of bags as well as the loading of luggage onto flights.

Airport operator BAA said yesterday that the software problems were "resolved" and the baggage system was "functioning well", after BAA worked through Saturday night tackling the issue.

But yesterday it admitted that issues were still being experienced with the technology, and a spokesperson confirmed BAA IT specialists were working with supplier Vanderlande Industries to solve them. Vanderlande was one of the key creators of the overall baggage system, alongside IBM and Alstec.

BA, the sole resident at Terminal 5, has begun to express its discontent at the way the systems problems are being resolved. At the weekend, the carrier was quick to place the blame on BAA, and on its website this morning it apologised to passengers, adding: "We are urging BAA to resolve these issues as soon as possible."

A spokesperson at the airline said the systems were BAA's responsibility to fix, not BA's. "Just because we're the only airline in the terminal doesn't mean we run the systems," he said.

Last week the baggage system experienced other problems, after log-on issues compounded problems with staff getting into the building to start work. Repeated calls to BA, BAA and IT suppliers associated with the baggage system either resulted in no meaningful information or in the companies referring to each other for comment on the initial problems.

In Terminal 5, baggage is marked with bar codes, instead of by RFID tags, and the codes show passenger names and flight details. The high-tech baggage system was heavily featured in Terminal 5's pre-opening publicity, and was created through 400,000 man hours of software engineering. It forms a key part of the £75m technology expenditure at the new terminal.