could impugn
Regular verb: impugn - impugned- impugned

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could impugn
you could impugn
he could impugn
we could impugn
you could impugn
they could impugn 	I could be impugning
you could be impugning
he could be impugning
we could be impugning
you could be impugning
they could be impugning	I could have impugned
you could have impugned
he could have impugned
we could have impugned
you could have impugned
they could have impugned	I could have been impugning
you could have been impugning
he could have been impugning
we could have been impugning
you could have been impugning
they could have been impugning	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not impugn
you could not impugn
he could not impugn
we could not impugn
you could not impugn
they could not impugn 	I could not be impugning
you could not be impugning
he could not be impugning
we could not be impugning
you could not be impugning
they could not be impugning	I could not have impugned
you could not have impugned
he could not have impugned
we could not have impugned
you could not have impugned
they could not have impugned	I could not have been impugning
you could not have been impugning
he could not have been impugning
we could not have been impugning
you could not have been impugning
they could not have been impugning	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I impugn?
could you impugn?
could he impugn?
could we impugn?
could you impugn?
could they impugn? 	could I be impugning?
could you be impugning?
could he be impugning?
could we be impugning?
could you be impugning?
could they be impugning? 	could I have impugned?
could you have impugned?
could he have impugned?
could we have impugned?
could you have impugned?
could they have impugned? 	could I have been impugning?
could you have been impugning?
could he have been impugning?
could we have been impugning?
could you have been impugning?
could they have been impugning? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not impugn?
could you not impugn?
could he not impugn?
could we not impugn?
could you not impugn?
could they not impugn? 	could I not be impugning?
could you not be impugning?
could he not be impugning?
could we not be impugning?
could you not be impugning?
could they not be impugning? 	could I not have impugned?
could you not have impugned?
could he not have impugned?
could we not have impugned?
could you not have impugned?
could they not have impugned? 	could I not have been impugning?
could you not have been impugning?
could he not have been impugning?
could we not have been impugning?
could you not have been impugning?
could they not have been impugning?