Chris Christie has stepped up his verbal attacks on Donald Trump as the former president faces fresh scrutiny over his handling of classified documents. The former New Jersey governor told the New York Times that Mr Trump was likely to become increasingly erratic as he tried to avoid being sent to prison. “He’s scared,” Mr Christie told the Times. “Look, a guy like him, the last place you ever want to be in life is in jail because you give up all control, and he’s a complete control freak.” Mr Christie spoke out after the ex-president was heard in a leaked tape bragging that he had kept documents about a military strike on Iran after leaving office that he knew were classified. Mr Trump has since rolled out several excuses about the audio, including that he was referring to plans for a golf course, and that he had merely engaged in “bravado”. “For Donald Trump, it is better to be called a liar than to go to jail,” Mr Christie added. “If what it buys him is a get-out-of-jail-free card, he’ll take that trade every day.” Mr Christie, who was among the first Republicans to endorse Mr Trump in 2016, is using his candidacy for the GOP presidential nomination to publicly flog his former ally at every opportunity. He told the Times that he expected Mr Trump would show up for presidential primary debates, despite his insistence that he would skip them. “His ego won’t permit him not to. He can’t have a big TV show that he’s not on,” Mr Christie said. Mr Trump is polling at 52 per cent in an average of GOP primary polls over the past six months by FiveThirtyEight.com. In a crowded field, Mr Christie has struggled to attract support and is seventh on 2.7 per cent. On Sunday, former Trump White House spokesperson Stephanie Grisham told MSNBC her former boss would regularly show classified documents to guests at the Mar-a-Lago dining room patio. “He has no respect for classified information [and] never did,” she said. Read More Trump news – live: Ex-Trump press secretary says she saw him show documents to Mar-a-Lago guests Trump’s own words about an indicted president come back to haunt him Ex-Trump spokesperson claims she saw him show off documents on Mar-a-Lago dining patio What's 'Bidenomics'? The president hopes a dubious nation embraces his ideas condensed into the term Chris Christie says McCarthy spoke correctly about Trump the first time Chris Christie attacks Trump for diverting campaign funds to legal battles Chris Christie tells ‘Adonis’ Trump to ‘look in the mirror’ after weight attacks