President Donald Trump’s personal lawyer warned Joe Scarborough that he “better have proof” to back up the claim that Trump himself leaked his tax returns to the journalist David Cay Johnston.

Michael Cohen, a longtime Trump associate and fixture on cable television, warned the MSNBC host after Scarborough said Trump had “cherry picked” a return to leak in order “to distract from Russia hearings and the Trumpcare meltdown.”

Scarborough – known in the past for his connections to Trump’s inner circle, and to the President himself – made the charge on his on his Twitter account Wednesday:

This one tax return is not bad for him because he cherry picked one return from over a decade ago and had it leaked to the press. https://t.co/P5cMuApGVe — Joe Scarborough (@JoeNBC) March 15, 2017

The Trump camp released one positive tax return to distract from Russia hearings and the Trumpcare meltdown. That’s painfully obvious. https://t.co/NLBVPJhwg6 — Joe Scarborough (@JoeNBC) March 15, 2017

Responding to Scarborough, Cohen did not dispute the claim:

.@JoeNBC As #potus @realDonaldTrump personal attorney, I know who has his taxes. You better have proof to back up your claim and big mouth! — Michael Cohen (@MichaelCohen212) March 15, 2017

Scarborough responded in kind:

And by the way “attorney”: 1. Read the First Amendment

2. Save your dumb thug routine for someone who gives a damn. https://t.co/EZfiaEq2yp — Joe Scarborough (@JoeNBC) March 15, 2017

Presenting two pages of Trump’s tax returns Tuesday night on MSNBC, journalist David Cay Johnston said he had received the document “over the transom.”

“And let me point out, it’s entirely possible that Donald sent this to me,” he added. “Donald Trump has, over the years, leaked all sorts of things.”

The document didn’t provide much information about the depth or extent of Trump’s financial entanglements, as Johnston has simply published the top two summary pages of Trump’s 2005 returns, though they did show Trump paid $38 million in taxes that year.

Cohen made headlines recently when he said he had served as a go-between for a pro-Russian Ukranian politician, who gave him a “peace plan” to resolve the conflict in Crimea to present to Trump. The New York Times reported in February that Cohen had hand-delivered the plan to then-National Security Adviser Michael Flynn’s office.