RSA yesterday told analysts and investors it's aiming "to be the number one" in the Irish market by the end of the year.
The challenge to Aviva's long-held status as Ireland's biggest insurer comes just six months after RSA's attempt to buy Aviva's Irish business collapsed.
Announcing its 2010 results, RSA struck an upbeat tone, saying that it was already the "second" biggest insurer in the market, rising from fifth position in 2008.
The surge followed RSA's acquisition of online brokerage 123.ie, which gives the UK insurer the right to offer renewals to all of 123.ie's customers.
RSA was also mooted as a bidder for Quinn Insurance Limited, but it is understood that the UK insurer is no longer a contender to buy the Cavan based insurer.
RSA said it had grown premium income by 7pc last year, out-performing a marginal fall in premiums across the market. RSA's outperformance was attributed to "rate, affinity deals and acquisitions".
The insurer said it had maintained a combined operating ratio -- a key measure of insurers' profitability -- at 90.9pc last year, comfortably within the profit/loss divider of 100pc.
German insurer Allianz also issued full-year results yesterday, but the data included scant Irish detail.