Premier Dalton McGuinty will today deliver the hard sell to some of the people most fearful of the new harmonized sales tax — Liberal MPPs worried about their jobs.

McGuinty will use an extraordinary caucus meeting being held this morning at the First Canadian Place offices of the Toronto Board of Trade to deliver a pointed presentation on how critical the HST is to Ontario’s economic future.

Sources told the Toronto Star the premier and Revenue Minister John Wilkinson will show MPPs — some of whom are fretting about losing their seats in the 2011 election over the 13 per cent tax — polling data and other information to allay concerns.

After a summer of struggling to explain the rationale behind the tax to constituents, and now facing a key Sept. 17 byelection in Toronto that is shaping up as an HST referendum, Liberal MPPs are skittish.

“If they can’t give me a 30-second sound bite on why this is a good thing to do then I’m screwed,” confided one Liberal MPP in a vulnerable seat.

The melding of the eight per cent provincial sales tax with the five per cent federal GST, which takes effect July 1, is designed to cut the costs for business by streamlining the system and placing more of the burden on consumers.

In London, Ont., yesterday, McGuinty acknowledged some blowback over the HST — including from within party ranks.

“Not a lot of folks are raising it with me, but I think there are some concerns — that’s fair to say. People are wondering about the necessity of doing it,” he told reporters.