The patience of investors snapped amid warnings in the City that many of RBS's targets for a return to health were a long way from being achieved.
Shares were 8% lower as the wider market also retreated on the back of fears over escalating tensions in the Ukrainian region of Crimea. The FTSE 100 was 46 points lower at 6752.7 as the top flight continued its retreat from close to a record high earlier in the week.
Part-nationalised RBS led the fallers board by some distance as its shares dived 30.25p to 323.75p, despite Mr McEwan's plans to slash the number of divisions to three and make savings under another swingeing cost-cutting drive.
IG client manager Will Hedden said: "It is still hard to see the light at the end of the tunnel of nationalisation as a sixth straight annual loss misses expectations and highlights the job that still remains.
"One has to feel that the continued political fever created by bonus-paying at the investment bank has kept many investors away."
RSA Insurance was also sharply lower after former RBS boss Stephen Hester axed the company's dividend and launched plans to raise £775 million through a rights issue equivalent to 20% of its market value.
With operating profits for 2013 down to £286 million from £601 million a year earlier, shares slumped 2.6p to 99.5p, a fall of 3%.
Other insurers were also under pressure as the sector counts the cost of a rising bill for flood claims and difficult conditions in the motor insurance market.
Aviva was 12.25p lower at 460.75p, while Admiral was 27p cheaper at 1421p.
Pensions and savings firm Standard Life was also under pressure - down 11.85p to 373.35p - after it announced a 13% fall in profits to £751 million, despite a 12% rise in assets under administration to £244.2 billion.
On a brighter note, shares in leisure group Whitbread rose after the Costa coffee and Premier Inn hotel chain operator said it expected to post full-year results towards the top end of expectations. Shares rose 149.5p to 4340.5p as it said like-for-like sales rose 6.8% in the 11 weeks to February 13.