England went down to a 184-run third Test defeat against Sri Lanka on Monday at Trent Bridge which saw the tourists end the three-match series level at 1-1.
Muttiah Muralitharan took eight for 70 as the home side slumped to 190 all out but former England opening batsman Boycott said the Sri Lanka off-spinner was not the only reason for the home side's defeat.
"England under-performed with bat and ball in the first innings," said Yorkshire great Boycott. "And their malaise began with an inability to knock over the Sri Lanka tail.
"England had Sri Lanka 138 for eight on the first afternoon but instead of finishing them off their bowlers suddenly became ineffective," he also wrote in his column in Tuesday's Daily Telegraph.
"Not getting rid of the tail hurt them at Lord's (the venue for the drawn series opener) where they ended up bowling 199 overs in the second innings
"England should have nailed them there, not pussyfooted around for 14 hours in the field."
Boycott, renowned for his concentration at the crease, also said too many of England's batsmen had given their wickets away and stressed that had been a particular problem at Trent Bridge.
"Murali only got three wickets in the first innings which means that six wickets fell on a good pitch to very average bowlers (Marcus Trescothick was run out). Five out of seven batsmen got starts yet nobody made a half-century."
Boycott, who played in several England sides that enjoyed Test series victories against Australia, was clear about the root cause of the current team's modest form.
"The problem since England won the Ashes is that everyone is still focused on last year and next winter," he said ahead of November's start to the next Anglo-Australian Test campaign.
"The players can pretend all they want but deep down they know they could have and should have beaten Sri Lanka 3-0," added Boycott, who added England coach Duncan Fletcher faced some tough decisions.
"This is where the coach has to earn his money. He believes in loyalty... Loyalty is very admirable up to a point but it has to be repaid with performances otherwise we are drifting into an Ashes series on indifferent form and indifferent results."