HSBC saw unexpected rise in profits despite the  Swiss leaks scandal Reuters

Europe's biggest bank HSBC said it will make a decision about whether to relocate outside the UK within months as it posted a surprise increase in first-quarter profits.

"It's going to take us a few months, not years," said Stuart Gulliver, the bank's chief executive. The bank's headquarter's have been based in the UK since 1993.

Gulliver made the comments as the bank reported a 4% rise in first-quarter profits for 2015, fuelled by surging revenue in its investment banking arm.

Those gains outweighed increased costs for compliance and regulation, helping the bank beat expectations of an overall loss for the first three months of the year.

HSBC's Swiss arm is at the centre of allegations it helped rich customers dodge tax, but the so-called Swiss leaks scandal had not hurt its balance sheet, Gulliver said.

The scandal has "undoubtedly done reputational damage to the firm" and "affected [employees'] sense of pride", Gulliver said. "It hasn't actually resulted in any significant decrease in business. We haven't seen in any of the business segments a significant change in business."