The move helped calm fears in the city after around £600m was wiped off the firm’s value as shares plunged from 191p over the week.
HSBC jbecomes its third corporate broker, joining Stifel and Morgan Stanley, and will help with Carillion’s comprehensive review of the business over the next two months.
The move saw shares creep up around 8% in early trading to around 59p.
The damaging profit warning and mounting debts, expected to hit £900m, leaves the firm fighting for survival.
Its options include include a debt-for-equity swap, a heavily dilutive equity raising from shareholders or a rescue takeover if a foreign buyer could be found.