RBS was today scrambling to fix another embarrassing IT glitch that left customers using its popular mobile app unable to access their accounts online.

Two million customers at the taxpayer-backed bank, which includes NatWest, have the app on smartphones and tablet computers, and many took to Twitter to express frustration after they were unable to use it to check their money.

It follows an IT fiasco last summer that saw payments go awry, wages appear to go missing and home purchases and holidays interrupted, and has already cost the bank £175m (€204m) in costs and compensation.

Today’s setback is the latest bump in the road for RBS, which is 81% publicly owned, as hopes rise that it can soon be returned to the private sector after being rescued at the height of the financial crisis.

Users went on Twitter to complain about the glitch on the Ulster Bank app.

#UlsterBank app down again. Can someone please remind me why im still with them!! — Brenny (@brenny1984) May 24, 2013

The latest annual results for RBS saw it record losses of £5.2bn (€6bn), driven by a £390m (€456m)settlement for rate-fixing, £1.1bn (€1.2bn) provision for mis-selling, and the IT problems of June and July 2012.

Today’s setback is particularly embarrassing as it is looking to shift its focus towards online customers.

Last week it announced that it was cutting 1,400 jobs in its retail arm as it moved investment into “things that matter most to customers” including mobile and online services.

It has been encouraging customers to use the technology, sending out tweets such as one two days ago which read: “Is it easy to pay someone with your bank’s mobile app? It’s simple with RBS.”

Frustrated customers this morning described how they tried to access the app but were told there was no internet connection – although other apps were working.

One said he had been logged out in the middle of a transaction. He received a response from RBS apologising and telling him to “try again later”.

Other Twitter users wrote:

Pointless having the #rbs app on my phone because it hardly ever works 😡 — Christine (@2Christinelamb) May 24, 2013

RBS Help responded on Twitter saying: “We’re aware of some issues on our Mobile Banking service and are working hard to fix them. Sorry and thanks for your patience.”

The bank’s press office tweeted:

Customers using the NatWest brand also appeared to be affected, according to Twitter comments, while some also appeared to be experiencing problems with the Ulster Bank app.