Fresh from their opening victory at St Helens, England looked intent on putting the series to bed from the outset on Saturday (Sunday AEDT) and had a two-try lead thanks to a pair of Ashton tries without reply in the first period.
Harry Smith's two penalties extended the score to 14 before Toluta'u Koula scored Tonga's solitary try of the afternoon, which was not enough to stop England from gaining an unassailable 2-0 series lead.
The Tongans, full of NRL talent, had hoped to be sharper after their opening defeat but actually provided a much less convincing display on a rain-soaked afternoon.
"Our discipline let us down we gave away too many penalties and when you do that you can't win Test matches," said Tongan coach Kristian Woolf, the Dolphins' assistant.
"Our last play wasn't great but Test match footy is about getting those things right.
"You don't get many opportunities to have a crack at their line so when you get good field position you have to make them pay a bit.
"But we're not throwing the towel in we've got one game to go and a young squad so we're only going to get better."
England picked up where they left off last weekend and opened the scoring in the sixth minute after the ball was spread from left to right, Ashton waiting in the corner to collect the ball and rush over the whitewash.
Tonga came close to a try as the ball went through the hands and Moses Suli unleashed Koula down the left but he was ushered into touch, which sparked a brawl between the two sets of players.
Manly winger Koula looked the main danger for the visitors and for a moment it looked like he had unlocked the English defence with a superb turn of foot before spilling the ball in touch.
Moments after Tonga were denied a reply on the try line, England went up the other end and scored their second try of the afternoon when Mikey Lewis's neatly threaded grubber fell beautifully for the onrushing Ashton who touched down for the second time.
England could have had a third try soon after the break when Mike McMeeken's kick found Tom Johnstone in acres of space but he dropped the ball with the try line at his mercy and had to settle for Smith's penalty to make it 14-0.
The away side were still looking for their first points of the game and almost had them when Isaiya Katoa's dummy freed Dion Teaupa up but Johnstone and Lewis brought him down to prevent a first try.
Tonga did most of the attacking in the second period and looked to break away once again when Tyson Frizell latched onto a long kick and set Tui Lolohea free with his sights on the whitewash, but Johnstone was on hand once again to bring those efforts to a halt.
A few seconds later, Tonga were awarded a penalty and finally had their first score of the game as the ball went through the hands and Koula was waiting on on the byline to storm over in the corner and reduce the deficit to 10 points.
But that was all they could muster as they suffered a second straight defeat with one Test match to play at Headingley.
