CARLTON has locked in one of its key defensive planks with Lachie Plowman inking a two-year extension.

The 23-year-old, who was already contracted until the end of next year, will now be at the club until at least the end of the 2020 season.

"Lachie has been a very dependable contributor for our backline since making his way to Ikon Park at the end of 2015 and we're delighted someone of his character and ability will be at our club for a further two years," Carlton head of football Andrew McKay told the club website.

"Under the guidance of Kade Simpson and Sam Docherty across the backline this year, Lachie has made the most of his opportunity in defence, managing 21 consecutive games for the first time in his career.

"We’ll be eager to see Lachie take his game to another level in 2018 and beyond as a key pillar in defence for our side."

Originally drafted by Greater Western Sydney with pick No.3 in the 2012 NAB AFL Draft, Plowman joined the Blues at the end of the 2015 season.

He has played 40 games in his two seasons at the club to take his career total to 60.