Bangladesh were 169-7 in the 42nd over and in deep trouble, despite the excellence of Mahmudullah top-scoring with 75. But Mortaza thumped two fours and three sixes in his 44 from 29 balls in a 69-run partnership with Nasir Hossain (27no) to lift the Tigers to 238 -8.
England will still be favourites to wrap up the series with a match to spare after a largely fine collective bowling performance, with two wickets apiece for Chris Woakes, Jake Ball and Yorkshire’s Adil Rashid, after the unchanged tourists opted to bowl first on a slow pitch.
Imrul Kayes had made centuries in the warm-up in Fatullah and the opening ODI against England but he contributed just 11 before pulling Woakes to deep square leg.
Woakes had his second wicket when Tamim Iqbal sent a shorter ball straight into the hands of Moeen Ali at midwicket before Sabbir Rahman’s tortuous innings of three off 21 balls was ended when he bottom-edged onto his stumps.
The crowd was stunned into silence although they were briefly stirred into life when Mahmudullah, promoted to four, and Mushfiqur Rahim rallied with a 50-run partnership from 51 balls.
Ball ended their resistance, though, taking his second wicket when Mushfiqur (21) top-edged a pull which landed in the hands of Moeen, running in from fine leg to take an excellent diving catch.
Mahmudullah brought up his half-century from 51 balls with a thin edge for his fourth four but Shakib Al Hasan, who registered 79 off 55 on Friday, was strangled down the leg side off Ben Stokes after making just three off 14 on Sunday.
Mahmudullah ensured there was no complete collapse as there had been in the first match but at 130-5 from 35 overs, Bangladesh needed a strong finish to set a competitive total.
Just as Mosaddek Hossain was starting to look comfortable at the crease after a nervy start, Bangladesh lost Mahmudullah, who was pinned in front attempting to sweep Rashid.
Mosaddek was out for 27 after pulling into the deep off a Rashid long hop although two straight sixes in a Moeen over from Mortaza roused a packed crowd under lights.
Some unorthodox strokes from Mortaza took Bangladesh beyond 200 as the captain and Nasir Hossain put on 50 in only 34 balls.
While Mortaza was run out in the final over, his lower order cameo at least spared his side embarrassment.