The full extent of the damage done to Liverpool by Luis Suarez's failure to shake Patrice Evra's hand at Old Trafford was revealed yesterday when it emerged that the managing director, Ian Ayre, received a "robust" call from the club's £20m shirt sponsor Standard Chartered on Sunday morning, in which the US bank expressed its concerns.

A corporate sponsor needing to question a player's conduct is rare in the extreme, though the call from a Standard Chartered director to Ayre reflects the bank's determination that its image should not be damaged by involvement in the sport. Standard's corporate affairs director Gavin Laws told The Independent last year that the bank had needed to establish that Liverpool had "the right set of responsibilities and guidelines for their players" before agreeing the record shirt deal.

A Standard source would not be drawn yesterday on whether Liverpool had been tackled on the Suarez case earlier in the 120-day saga, which began when Suarez racially abused the Manchester United defender during a match, or whether the bank was happy with the three apologies which emanated from Anfield on Sunday afternoon. But the call went in to Anfield, rather than to the club's American owners, Fenway Sports Group, whose intervention forced a humbling apology from Suarez and his manager, Kenny Dalglish. "We speak on a regular basis about a number of things and we are very clear that management of players is down to the club," a bank source said. "We confirmed that we were disappointed about what happened on Saturday and the club listened to us. The club has kept us informed throughout about what they are doing."

Liverpool are entitled to fine Suarez, under the terms of his contract, though any decision to do so appears to depend on whether the club's American owners believe that the contrition shown on Sunday has sufficiently repaired the club's battered reputation.

The club's internal inquiry into Suarez's conduct at Old Trafford on Saturday is likely to centre on whether Suarez was actually ordered to shake the Manchester United defender's hand. If such an instruction had been handed down to him by Dalglish, then the Uruguayan would be in breach of section 3.1.6 of his contract, "to comply with and act in accordance with all lawful instructions of any authorised official of the club".

There is a significant difference between Liverpool asking Suarez if he would be prepared to shake Evra's hand and ordering him to do so and if Liverpool had been merely relying on him keeping his word that he would enter into the handshake, then the club's position in disciplining him would be weakened. But Suarez may also be deemed to have brought the club and football into disrepute, in contravention of article 3.2.5 of his contract.

Further punishment for Suarez, to go with the humiliation of having the club declare publicly that he had, in effect, lied when he said he would shake Evra's hand, risks causing further damage to the relationship between club and player, and heighten the risk of Suarez leaving Anfield this summer. Dalglish is likely to want to avoid a fine and, if Fenway Sports Group insists on such a punishment, the club are likely to pursue some of the compromise strategies generally used in the game to prevent a further fracturing of the relationship.

It is highly likely that Suarez would be consulted about such a decision and told that Liverpool have no other option. Liverpool may also suspend half or all of any fine handed down, until the end of the season, leaving Suarez on notice.

Liverpool's delay in resolving the issue of a financial penalty was due to uncertainties about the contractual position, but Neil Johnston, an employment specialist at the law firm Field Fisher Waterhouse, said: "He was in breach if he was told to shake hands. There is a potential argument that, even if the player was not instructed to shake hands, he has done something that has brought his club into disrepute."

There are no plans at the Premier League to review whether teams should shake hands during match preliminaries, with the League of the view that players are generally willing to show respect for each other. There was no debate at the League about whether to cancel the ceremony for Saturday's game, as the FA had done for the QPR-Chelsea FA Cup tie, because of the John Terry-Anton Ferdinand case. The League does not anticipate the handshake becoming an issue until the Chelsea-QPR game on 28 April.